Manufacture of three dimensional objects from thermosets

ABSTRACT

A method for creating a three dimensional (3D) object from reactive components that form a thermoset product. In one embodiment, a method includes providing first and second reactive components that are effective to form the thermoset product. In one embodiment, the thermoset product includes a urethane and/or urea-containing polymer. In one embodiment, the first reactive component includes an isocyanate and the second reactive component includes a polyol having at least one terminal hydroxyl group, a polyamine having at least one amine that includes an isocyanate reactive hydrogen, or a combination of the polyol and the polyamine. In one embodiment, the first reactive component includes a prepolymer, and optionally the ratio of viscosity of the first and second reactive components is from 1:3 to 3:1. Also provided is a 3D object that includes a completely reacted thermoset product, and a thermoset system that includes a first and a second reactive component.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser.No. 62/430,919, filed Dec. 6, 2016, and U.S. Provisional ApplicationSer. No. 62/524,214, filed Jun. 23, 2017, each of which are incorporatedby reference herein.

TECHNICAL FIELD OF THE INVENTION

This invention includes, but is not limited to, to formulations andmethods for three dimensional printing using thermoset compositions suchas, but not limited to, polyurethane.

BACKGROUND

Fused filament fabrication (FFF), also referred to in the art asthermoplastic extrusion, plastic jet printing (PJP), fused filamentmethod (FFM), or fusion deposition modeling, is an additivemanufacturing process wherein a material is extruded in successivelayers onto a platform to form a 3-dimensional product. Typically, FFFuses a melted thermoplastic material that is extruded onto alower-temperature platform. Three-dimensional printing (“3D printing”)often uses support structures which are easily dissolved or removed fromthe part after it is finished. Disadvantages of existing FFF technologythat uses thermoplastics include, but are not limited to, singlematerial property printing, print-direction strength, limiteddurability, and limited softness. In contrast, thermosetting materialsdescribed herein have not been used in FFF because prior to cure themonomers are low viscosity liquids, and upon deposition the curingliquid flows or breaks into droplets, resulting in finished parts of lowquality and undesirably low resolution. In practice, attempts to printwith thermoset materials has required addition of fillers (such asinorganic powders or polymers) to induce thixotropic behavior in theresin before it is fully cured. These solutions affect the finalproperties of the printed part. Other problems include poor resolutioncontrol in the printed part and frequent clogging of mixing systems.

SUMMARY OF THE APPLICATION

The present disclosure provides a solution to one or more of theproblems and/or disadvantages described above. The additivemanufacturing process described herein can be referred to as extrudedthermoset printing (ETP).

As used herein, the terms “thermoset,” “thermoset product,” and“thermoset material” are used interchangeably and refer to the reactionproduct of at least two chemicals which form a covalently bondedcrosslinked or polymeric network. In contrast to thermoplastics, athermoset product described herein may irreversibly solidify or set.

In certain embodiments, a solid polymer, (e.g., a polyurethane)described herein is an elastomer. An elastomer is a polymer (e.g., apolyurethane) that is deformable when stress is applied, but retains itsoriginal shape after the stress is removed.

As used herein, the term “layer” refers to a strand of thermoset productthat has been extruded from an extrusion nozzle and deposited on, forinstance, a substrate. A layer is initially a partially reactedthermoset product, and cures to become a completely reacted thermosetproduct.

As used herein, the term “partially reacted thermoset product” refers toa covalently bonded crosslinked or polymeric network that is stillreactive, e.g., it still has hydroxyl, amine, and/or isocyanatefunctionality that gives a measureable hydroxyl number, NH number, orNCO number in a titration. In another embodiment, a partially reactedthermoset product is a thermoset product that has a viscosity below3,000,000 cp. In one embodiment, a partially reacted thermoset productis a thermoset product that has a molecular weight of no greater than100,000 g/mol. A completely reacted thermoset product is a covalentlybonded crosslinked or polymeric network that has no measurable reactivegroups (e.g., hydroxyl, amine, or isocyanate functionality). In anotherembodiment, a completely reacted thermoset product is one that is asolid and has no measurable viscosity.

Layer resolution is the profile, (e.g., height) for a layer. Forinstance, extruding a layer from a nozzle having a diameter of 1millimeter (mm) results in a layer resolution that is 1 millimeter(e.g., 1 millimeter height). As used herein, the term “predeterminedlayer resolution” refers to the height of a layer and can be based onthe height of the nozzle above the printing substrate and the size ofthe nozzle used to extrude the layer. A “predetermined layer resolution”includes a tolerance for spreading of a layer after the layer ofthermoset product is extruded from a nozzle. Spreading of a layer afterit is deposited on a substrate or another layer may, in someembodiments, result in a decrease of the height of the layer from thetime it is deposited on the substrate. In one embodiment, a layer canspread so that the height of the layer decreases by no greater than 1%,no greater than 5%, no greater than 10%, no greater than 15%, no greaterthan 20%, no greater than 25%, no greater than 30%, no greater than 50%,or no greater than 75% of height of the layer when extruded. Forinstance, a layer having a height of 1 mm can spread so that the heightof the layer decreases by no greater than 5%, resulting in layer that is0.95 mm to 1 mm in height. The amount of spreading is determined whenthe thermoset of a layer is completely reacted. The predetermined layerresolution can be controlled by the height of the nozzle above thesubstrate, by the nozzle diameter, or a combination thereof. In oneembodiment, the predetermined layer resolution is controlled by thesmaller of the height of the nozzle above the substrate or the nozzlediameter. Suitable nozzles include but are not limited to those havingan inner diameter at the tip of 0.01 to 2 mm, or having an equivalentcross-sectional area when a nozzle is used that is not round.

As used herein, the term “predetermined shape resolution” refers to theshape of a three dimensional object (3D object) made using a methoddescribed herein.

The inventor herein identified a problem which exists because theinitial viscosities of commercially available thermoset startingmaterials after mixing are too low, and the commercially availablethermoset starting materials are designed to allow the reaction mixtureto flow and fill molds. However, this is the opposite of what is neededfor ETP 3D printing. Provided herein is a process and system forgenerating a 3D object by forming successive layers of curing thermosetmaterial, each successive layer forming covalent bonds with, andadhering to, the previously deposited layer, to define the desired 3Dobject having a predetermined shape resolution. Many types of objectforms can be created with the techniques described herein. Complex formsare more easily created by using the functions of a computer to helpgenerate the programmed commands and to then send the program signals tothe object forming subsystem. Open-source software packages forconverting 3-dimensional objects from CAD files into “slicer” STL filesfor defining the layers of the object and software to control theprinter are available to the skilled person and routinely used.Geometries of such complex forms are available which cannot be easilyconfigured with molds. In one embodiment, the covalent bonds betweenlayers consists of bonds formed between the partially reacted thermosetproduct, e.g., an adhesive is not added during the method and anadhesive does not exist between layers deposited during the creation ofthe object. In one embodiment, a complex geometry can built in a singleprocess step without first building multiple parts which must beassembled and joined together. In another embodiment, a part withregions of differing material properties can be built in a singleprocess without first building multiple parts from varied materials andthen assembled and joined together.

In one broad aspect, this disclosure provides a method of creating athree dimensional object from reactive components that form thermosetproducts using ETP, comprising: providing first and second reactivecomponents which have molecular weights and viscosities that areeffective to form a given part resolution, e.g., a predetermined layerresolution, during the method; introducing the first and second reactivecomponents into a mixing chamber where mixing occurs and wherein thefirst and second reactive components have a residence time in the mixingchamber and/or extrusion nozzle effective to meet the desiredpredetermined layer resolution, wherein the first and second reactivecomponents have a residence time in the mixing chamber insufficient tocompletely react, so that the mixture of the first and second reactivecomponents forms a partially formed thermoset composition, e.g., apartially reacted thermoset product, in the mixing chamber; extrudingthe partially reacted thermoset product out of the mixing chamberthrough an extrusion nozzle and onto a substrate, such as a stage or alayer of previously formed and partially reacted thermoset product; andmoving the extrusion nozzle and/or the substrate (relative to eachother) to sequentially deposit layers of partially reacted thermosetproduct to form a 3D object having a predetermined shape resolution. Inone embodiment, a partially reacted thermoset product is extruded out ofthe mixing chamber through an extrusion nozzle and onto a layer ofpreviously formed and completely reacted thermoset product.

In one broad aspect, this disclosure provides a method of creating a 3Dobject from reactive components that form thermoset products using ETP,including: providing first and second reactive components that areeffective to form a thermoset product having a predetermined layerresolution during the method; introducing the first and second reactivecomponents into a mixing chamber where mixing occurs to form a mixture,wherein the first and second reactive components have a residence timein a mixing chamber effective to form a partially reacted thermosetproduct in the mixing chamber and result in the predetermined layerresolution upon exiting the mixing chamber, wherein the first and secondreactive components have a residence time in the mixing chamberinsufficient to completely react; extruding the partially reactedthermoset product out of the mixing chamber through an extrusion nozzleand onto a substrate, such as a stage or a layer of previously formedthermoset; and moving the extrusion nozzle and/or the substrate to forma 3D object having a predetermined shape resolution, wherein the layersof thermoset are deposited sequentially by moving the extrusion nozzleand/or the substrate to form a desired three dimensional object. Inanother broad respect, this disclosure provides an apparatus forcreating a three dimensional object from reactive components that form athermoset product, comprising: an automatically moveable extrusionnozzle; first and second containers adapted for holding first and secondreactive components; and a stage for receiving a partially reactedthermoset product resulting from the mixing of the first and secondcomponents. In one embodiment, the first and second components havemolecular weights and viscosities that are effective to form a layerhaving a predetermined layer resolution for the three dimensionalobject. In another embodiment, the first and second reactive componentsare effective to form a thermoset product having a predetermined layerresolution as it is extruded through an extrusion nozzle. Optionally,additional containers of reactive components may be incorporated inorder to provide a wider range of final polymers; additional containersmight also contain catalysts, water, or other reactants which can bevaried. Optionally, an apparatus also permits control of the amounts ofthe first and second reactive components that are combined to form athermoset product having a predetermined layer resolution. An apparatususeful herein also includes the ability to maintain a precise meteringof the reactant components so that a ratio of the first and secondreactive components, or additional reactive components (e.g., a thirdreactive component), are mixed. Altering the amounts of additionalcomponents, e.g., a third, fourth, or fifth component, during productionof a 3D object can result in a 3D object having one or more propertiesvary between different areas of the 3D object. For instance, thehardness, density, durability, or a combination thereof, can changebetween two different areas of the 3D object.

In this disclosure, a thermoset product is made from reactive componentsthat have viscosities and components having molecular weights such thatthey can be used to make a 3D object with the required objectresolution. In another embodiment, the thermoset product is made fromreactive components that are effective to form the thermoset producthaving a predetermined layer resolution upon extrusion from an extrusionnozzle.

In the practice of this disclosure, a mixing chamber is used with aconfiguration such that the two or more reactive components areintimately mixed, and with a residence time and optional catalyst levelsuch that the reaction is extended far enough at the time of extrusionfrom an extrusion nozzle that the material can maintain the requiredresolution (e.g., the predetermined layer resolution). The reactivecomponents can also be selected to facilitate mixing with minimalagitation (such as, but not limited to, use of static mixers) where thereactive components have similar characteristics, such as similarviscosities, similar chemical compatibility, or a combination thereof.

In one embodiment, the two reactive components are designed to includefast reactants and corresponding catalysts so that upon mixing theresulting thermoset product quickly exceeds required characteristics(e.g., viscosity) for predetermined layer resolution, but also designedto include slow reactants (e.g., in one embodiment, some slower reactingisocyanate and/or polyol functionalities) and corresponding catalysts sothat the mixture is not completely reacted (i.e., it is a partiallyreacted thermoset product, not a completely reacted thermoset) at thetime that the next layer is applied, thus bringing strong adhesionbetween layers. In other embodiments, the two reactive components aredesigned to include fast reactants and corresponding catalysts, or slowreactants and corresponding catalysts. “Fast” reactants refers toreactive components that react quickly enough to increase viscosityimmediately (e.g., within 1 second after mixing) and form a partiallyreacted thermoset product that maintains its layer resolution afterdeposition on a substrate or a previously deposited layer of thermosetproduct. “Slow” reactants refers to reactive components that can beginto react after it is deposited and result in the final completelyreacted thermoset product. The relative reaction speeds of variousreactive components that produce polymers (e.g., polyurethanes) areknown to the skilled person. For instance, aliphatic isocyanates aretypically slower than aromatic isocyanates, methylene diphenyldi-isocyanates (MDI) are generally faster than toluene di-isocyanates(TDI), and one isocyanate on isophorone diisocyanate (IPDI) is muchslower than the other. Fast reacting components include chain extenders,including but not limited to di-amine, water, and compounds that includea primary hydroxyl reaction group.

Fast and slow reactants can be in the same reactive component or indifferent reactive components. When both fast and slow reactants are inthe same reactive component, the reactive component can be one thatincludes an isocyanate or one that includes a polyol. In one embodiment,the reactive component containing a polyol contains a fast reactant, aslow reactant, and a polyol and/or polyamine prepolymer, and that otherreactive component includes at least one type of monomeric isocyanateand an isocyanate prepolymer. In one embodiment, one or more fastreactants can make up from 1% to 20% (wt %) of a reactive component. Inone embodiment, one or more slow reactants can make up from 50% to 99%(wt %) of a reactive component.

In one embodiment, temperature can also be used to alter characteristics(e.g., viscosity) of the partially reacted thermoset product as it exitsthe extrusion nozzle, or to speed the reaction upon contacting thesubstrate or a previously deposited layer of thermoset product. Theoperating temperature of the printing environment, e.g., the reactants,the mixing chamber, the nozzle, the substrate, and/or the air of thechamber in which an object is created, can be from 0° C. to 150° C. Theskilled person will recognize suitable operating temperatures can varydepending upon the thermoset. For instance, some polyester polyols aresolid at room temperature, thus higher operating temperatures can beuseful when creating an object with a polyester polyol.

In the practice of this disclosure, a composition can be employedwherein the segment lengths can be systematically altered to provide achange in mechanical properties (e.g., from flexible to hard, from solidto foam, or a combination thereof) during the deposition. As usedherein, “segment length” refers to the smallest molecular weightsbetween the linkage points (urethane, urea, etc.). For instance, use ofa specific polyol results in a segment length based on the presence ofthat polyol in the polymer.

In one embodiment of this disclosure, a foam is 3D printed byco-extruding first and second reactive components effective to form athermoset product and produce a gas when they come into contact. Forexample, a reactive component can be used which contains isocyanateswith a second reactive component containing a blowing agent. A blowingagent is a compound that is capable of producing a cellular structure ina partially reacted thermoset product. Examples of blowing agentsinclude chemical blowing agents, such as water, and physical blowingagents, such as Freon and other chlorofluorocarbons,hydrochlorofluorocarbons, and alkanes.

The term “and/or” means one or all of the listed elements or acombination of any two or more of the listed elements.

The words “preferred” and “preferably” refer to embodiments of thedisclosure that may afford certain benefits, under certaincircumstances. However, other embodiments may also be preferred, underthe same or other circumstances. Furthermore, the recitation of one ormore preferred embodiments does not imply that other embodiments are notuseful, and is not intended to exclude other embodiments from the scopeof the disclosure.

The terms “comprises” and variations thereof do not have a limitingmeaning where these terms appear in the description and claims.

It is understood that wherever embodiments are described herein with thelanguage “include,” “includes,” or “including,” and the like, otherwiseanalogous embodiments described in terms of “consisting of” and/or“consisting essentially of” are also provided.

Unless otherwise specified, “a,” “an,” “the,” and “at least one” areused interchangeably and mean one or more than one.

Also herein, the recitations of numerical ranges by endpoints includeall numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2,2.75, 3, 3.80, 4, 5, etc.).

Reference throughout this specification to “one embodiment,” “anembodiment,” “certain embodiments,” or “some embodiments,” etc., meansthat a particular feature, configuration, composition, or characteristicdescribed in connection with the embodiment is included in at least oneembodiment of the disclosure. Thus, the appearances of such phrases invarious places throughout this specification are not necessarilyreferring to the same embodiment of the disclosure. Furthermore, theparticular features, configurations, compositions, or characteristicsmay be combined in any suitable manner in one or more embodiments.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a schematic of a polymer chemistry approach for developing3D printable polyurethane precursors for production of non-foams. Withconventional polyurethane foam precursor formulas, the initial viscosityis too low to print. As described herein, reaction components can bepre-reacted to form a high viscosity, printable formula and create abroad processing window for printing.

FIG. 2 shows the viscosity growth of the TDI-based formula (top lefttrace) and the MDI-based formula (bottom right trace). Viscometersettings: 22C, spindle 27, 0.3 RPM.

FIG. 3 shows the viscosity growth of the slow formula system of Example7.

FIG. 4 shows a fast formula processing window. The values in columns 1,2, 3, 4, 5, and 6 refer to a flow rate of millimeters per minute(mm/min).

FIG. 5 shows a slow formula processing window. The values in the columns1, 2, 3, and 4 refer to a flow rate of millimeters per minute (mm/min).

FIG. 6 shows a 3D object created as described in Example 8.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present disclosure provides methods that use the principles ofcomputer generated graphics to simultaneously execute CAD and CAM, andto produce 3D objects directly from computer instructions. Such methodscan be used to sculpture models and prototypes in a design phase ofproduct development, or as a manufacturing tool, or even to produce artforms.

In the extruded thermoset printing (ETP) method of the presentdisclosure the generation of individual solid or foam laminae (alsoreferred to herein as layers) representing cross-sections of a 3D objectis accomplished. The successively formed adjacent layers form thedesired 3D object which has been programmed into the system. Hence, thesystem of the present disclosure generates 3D objects by extrudingmaterial in a pattern according to a cross-sectional pattern of theobject to be formed at a selected surface of a reactive thermosetcomposition, e.g., a surface of a partially reacted thermoset product.Successive adjacent layers, representing corresponding successiveadjacent cross-sections of the object, are automatically formed andintegrated together (e.g., crosslinked by covalent bonds) to provide astep-wise laminar or thin layer buildup of the object, whereby a 3Dobject is formed and drawn from successively deposited substantiallyplanar or sheet-like surfaces of the fluid medium during the formingprocess, where the 3D object has a predetermined shape resolution.

The process employs a fluid reactive composition including, but notlimited to, first and second reactive components. The reactivecomposition is capable of forming thermoset compositions such aspolyurethanes.

As used herein, a “reactive component” refers to a composition thatincludes at least one chemical that can react with another chemical toresult in a thermoset product. In one embodiment, a reaction describedherein includes mixing a first reactive component with a second reactivecomponent to result in a thermoset product. A “reactive component” canalso, and typically does, include one or more components that do notreact to result a thermoset product. Thus, it is understood that not all“reactive components” are reactive per se. Non-limiting examples ofcomponents that do not react to result a thermoset product includecertain additives (e.g., certain catalysts), a solvent, and the like.

In one embodiment, the thermoset is a urethane and/or urea-containingpolymer. In one embodiment, as used herein a “urethane and/orurea-containing polymer” is a polymer which contains urethane groups(—NH—(C═O)—O—) as part of the polymer chain. In general, a urethanelinkage is formed by reacting isocyanate groups (—N═C═O) with hydroxylgroups (—OH). A polyurethane is produced by the reaction of anisocyanate containing at least two isocyanate groups per molecule with acompound having terminal hydroxyl groups. In one embodiment, anisocyanate having, on average, two isocyanate groups per molecule isreacted with a compound having, on average, at least two terminalhydroxyl groups per molecule.

In one embodiment, as used herein a “urethane and/or urea-containingpolymer” is a polymer which contains urea groups (—NH—(C═O)—NH—) as partof the polymer chain. In general, a urea linkage is formed by reactingisocyanate groups (—N═C═O) with amine groups (e.g., —N(R′)₂), where eachR′ is independently hydrogen or an aliphatic and/or cyclic group(typically a (C1-C4)alkyl group)). A polyurea is produced by thereaction of an isocyanate containing at least two isocyanate groups permolecule with a compound having terminal amine groups.

As used herein, “aliphatic group” refers to a saturated or unsaturatedlinear or branched hydrocarbon group. This term is used to encompassalkyl (e.g., —CH₃) (or alkylene if within a chain such as —CH₂—),alkenyl (or alkenylene if within a chain), and alkynyl (or alkynylene ifwithin a chain) groups, for example. As used herein, “alkyl group”refers to a saturated linear or branched hydrocarbon group including,for example, methyl, ethyl, isopropyl, t-butyl, heptyl, dodecyl,octadecyl, amyl, 2-ethylhexyl, and the like. As used herein, “alkenylgroup” refers to an unsaturated, linear or branched hydrocarbon groupwith one or more carbon-carbon double bonds, such as a vinyl group. Asused herein, “alkynyl group” refers to an unsaturated, linear orbranched hydrocarbon group with one or more carbon-carbon triple bonds.Unless otherwise indicated, an aliphatic group typically contains from 1to 30 carbon atoms. In some embodiments, the aliphatic group contains 1to 20 carbon atoms, 1 to 10 carbon atoms, 1 to 6 carbon atoms, 1 to 4carbon atoms, or 1 to 3 carbon atoms.

As used herein, “cyclic group” refers to a closed ring hydrocarbon groupthat is classified as an alicyclic group, aromatic group, orheterocyclic group, and can optionally include an aliphatic group. Asused herein, “alicyclic group” refers to a cyclic hydrocarbon grouphaving properties resembling those of aliphatic groups. As used herein,“aromatic group” or “aryl group” refers to a mono- or polynucleararomatic hydrocarbon group. As used herein, “heterocyclic group” refersto a closed ring hydrocarbon in which one or more of the atoms in thering is an element other than carbon (e.g., nitrogen, oxygen, sulfur,etc.). Unless otherwise specified, a cyclic group often have 6 to 20carbon atoms, 6 to 18 carbon atoms, 6 to 16 carbon atoms, 6 to 12 carbonatoms, or 6 to 10 carbon atoms.

In one embodiment, as used herein a “urethane and/or urea-containingpolymer” is a polymer which contains both urethane and urea groups aspart of the polymer chain. A polyurethane/polyurea is produced by thereaction of an isocyanate containing at least two isocyanate groups permolecule with a compound having terminal hydroxyl groups and a compoundhaving terminal amine groups. In one embodiment, a polyurethane/polyureais produced by the reaction of an isocyanate containing at least twoisocyanate groups per molecule with a compound having terminal hydroxylgroups and terminal amine groups (e.g., a hydroxyl-amine such as3-hydroxy-n-butylamine (CAS 114963-62-1)). Optionally and preferably, areaction to make a polyurethane, a polyurea, or a polyurethane/polyureaincludes other additives, including but not limited to, a catalyst, achain extender, a curing agent, a surfactant, a pigment, or acombination thereof.

An isocyanate, which is typically considered a polyisocyanate, has thestructure R—(N═C═O)—, where n is at least 2, at least 3, at least 4, atleast 5, at least 6, at least 7, or at least 8, and where R is analiphatic and/or cyclic group. In one embodiment, an isocyanate has an nthat is equivalent to n in Methylene diphenyl diisocyanate (MDI). In oneembodiment, the isocyanate is a di-isocyanate (R—(N═C═O)₂ or(O═C═N)—R—(N═C═O)).

Examples of isocyanates include, but are not limited to, methylenediphenyl diisocyanate (MDI) and toluene diisocyanate (TDI). Examples ofMDI include, but are not limited to, monomeric MDI, polymeric MDI, andisomers thereof. Examples of isomers of MDI having the chemical formulaC₁₅H₁₀N₂O₂ include, but are not limited to, 2,2′-MDI, 2,4′-MDI, and4,4′-MDI. Examples of isomers of TDI having the chemical formulaC₉H₆N₂O₂ include, but are not limited to, 2,4-TDI and 2,6-TDI. Otherexamples of isocyanates include, but are not limited to, monomericdiisocyanates and blocked polyisocyanates. Examples of monomericdiisocyanates include, but are not limited to, hexamethylenediisocyanate (HDI), methylene dicyclohexyl diisocyanate or hydrogenatedMDI (HMDI), and isophorone diisocyanate (IPDI). One example of a HDI ishexamethylene-1,6-diisocyanate. One example of a HMDI isdicyclohexylmethane-4,4′diisocyanate. Blocked polyisocyanates aretypically based on HDI or IDPI. Examples of blocked polyisocyanatesinclude, but are not limited to, HDI trimer, HDI biuret, HDI uretidione,and IPDI trimer.

Other examples of isocyanates that can be used for producing a thermosetdescribed herein include, but are not limited to, aromaticdiisocyanates, such as a mixture of 2,4- and 2,6-tolylene diisocyanates(TDI), diphenylmethane-4,4′-diisocyanate (MDI),naphthalene-1,5-diisocyanate (NDI), 3,3′-dimethyl-4,4′-biphenylenediisocyanate (TODI), crude TDI, polymethylenepolyphenyl isocyanurate,crude MDI, xylylene diisocyanate (XDI) and phenylene diisocyanate;aliphatic diisocyanates, such as 4,4′-methylene-biscyclohexyldiisocyanate (hydrogenated MDI), hexamethylene diisocyanate (HMDI),isophorone diisocyanate (IPDI) and cyclohexane diisocyanate(hydrogenated XDI); and modified products thereof, such asisocyanurates, carbodiimides and allophanamides.

A compound having terminal hydroxyl groups (R—(OH)—), where n is atleast 2 (referred to herein as “di-functional”), at least 3 (referred toherein as “tri-functional”), at least 4, at least 5, at least 6, atleast 7, at least 8, at least 9, and no greater than 10, where R is analiphatic and/or cyclic group, is referred to herein as a “polyol.” Theskilled person will recognize that a polyol mixture will often include asmall amount of mono-functional compounds having a single terminalhydroxyl group.

Examples of polyols include, but are not limited to, polyester polyolsand polyether polyols. Examples of polyester polyols include, but arenot limited to, those built from condensation of acids and alcohols.Specific examples include those built from phthalic anhydride anddi-ethylene glyol, phthalic anhydride and di-propylene glycol, adipicacid and butane diol, or succinic acid and butane or hexane diol. Theskilled person will recognize that many polyester polyols aresemi-crystalline. Examples of polyether polyols include, but are notlimited to, those built from polymerization of an oxide such as ethyleneoxide, propylene oxide, or butylene oxide from an initiator such asglycerol, di-propylene glycol, TPG (tripropylene glycol), castor oil,sucrose, or sorbitol.

Other examples of polyols include, but are not limited to, polycarbonatepolyols and lactone polyols such as polycaprolactone. In one embodiment,a compound having terminal hydroxyl groups (R—(OH)—) has a molecularweight (calculated before incorporation of the compound having terminalhydroxyl groups into a polymer) of from 200 Daltons to 20,000 Daltons,such as from 200 Daltons to 10,000 Daltons.

A compound having terminal amine groups (e.g., R—(N(R′)₂)_(n)), where nis at least 2, at least 3, at least 4, at least 5, at least 6, at least7, at least 8, at least 9, and no greater than 10, where R is analiphatic and/or cyclic group, and where each R′ is independentlyhydrogen or an aliphatic and/or cyclic group (typically a (C1-C4)alkylgroup), is referred to herein as a “polyamine.” The skilled person willrecognize that a polyamine mixture will often include a small amount ofmono-functional compounds having a single terminal amine group.

A suitable polyamine can be a diamine or triamine, and is preferablyeither a primary or secondary amine. In one embodiment, a compoundhaving terminal amine groups has a molecular weight (calculated beforeincorporation of the compound having terminal hydroxyl groups into apolymer) of from 30 Daltons to 5000 Daltons, such as from 40 Daltons to400 Daltons.

Examples of polyamines include, but are not limited to, diethyltoluenediamine, di-(methylthio)toluene diamine,4,4′-methylenebis(2-chloroaniline), and chain extenders available underthe trade names LONZACURE L15, LONZACURE M-CDEA, LONZACURE M-DEA,LONZACURE M-DIPA, LONZACURE M-MIPA, and LONZACURE DETDA.

Other examples of suitable polyamines include, but are not limited to,ethylene diamine, 1,2-diaminopropane, 1,4-diaminobutane,1,3-diaminopentane, 1,6-diaminohexane, 2,5-diamino-2,5-dimethlhexane,2,2,4- and/or 2,4,4-trimethyl-1,6-diaminohexane, 1,11-diaminoundecane,1,12-diaminododecane, 1,3- and/or 1,4-cyclohexane diamine,1-amino-3,3,5-trimethyl-5-aminomethyl-cyclohexane, 2,4- and/or2,6-hexahydrotoluylene diamine, 2,4′ and/or 4,4′-diaminodicyclohexylmethane, and 3,3′-dialkyl-4,4′-diamino-dicyclohexyl methanes such as3,3′-dimethyl-4,4-diamino-dicyclohexyl methane and3,3′-diethyl-4,4′-diaminodicyclohexyl methane; aromatic polyamines suchas 2,4- and/or 2,6-diaminotoluene and 2,6-diaminotoluene and 2,4′ and/or4,4′-diaminodiphenyl methane; and polyoxyalkylene polyamines.

Unless stated otherwise, the term “polyol and/or polyamine mixture”refers to a mixture of one or more polyols of varied molecular weightsand functionalities, one or more polyamines of varied molecular weightsand functionalities, or a combination of one or more polyols and one ormore polyamines.

The present disclosure also provides the compositions described hereinand a thermoset system comprising the compositions, e.g., a firstreactive component and a second reactive component, and one or moreoptional reactive components, such as a third reactive component.

The methods for making a thermoset product described herein, such as aurethane and/or urea-containing polymer thermoset product, includeintroducing first and second reactive components into a mixing chamber.In one embodiment, the first reactive component includes an isocyanateand the second reactive component includes a polyol and/or polyaminemixture. Thus, in one embodiment, the first reactive component includesan isocyanate and the second reactive component includes a polyol. Inone embodiment, the first reactive component includes an isocyanate andthe second reactive component includes a polyamine. In one embodiment,the first reactive component includes an isocyanate and the secondreactive component includes a polyol and a polyamine. The first andsecond reactive components have certain characteristics including, butnot limited to, viscosity, reactivity, and chemical compatibility.

Viscosity refers to a measure of a fluid's resistance to gradualdeformation by shear stress or tensile stress. In one embodiment,viscosity of a first reactive component and a viscosity of a secondreactive component can be at least 60 centipoise (cP). Typically, afirst reactive component and a second reactive component are formulatedwith prepolymers so that each component has a viscosity that is from 500cp to 500,000 cp. In one embodiment, the viscosity range of eachcomponent is from 2,000 cp to 5,000 cp. While it is expected that thereis no upper limit to viscosity, in one embodiment an upper limit may beno greater than 3,000,000 cp, no greater than 100,000 cp, or no greaterthan 50,000 cp. Viscosity is measured using a Brookfield viscometerusing spindle 27, sample cup SC4-13RD, and at a rotational speed with atorque % between 10 and 90%. A person of ordinary skill in the art willalso recognize that viscosity of a mixture can be further altered byincluding additives such as, but not limited to, thickeners,plasticizers, and solvents, or by changing temperature.

Chemical compatibility refers to the ability of the two reactivecomponents to intimately mix and result in a homogenous mixture orsolution. For instance, two aqueous solutions are chemically compatible,and two solutions of organic solvents are chemically compatible;however, an aqueous solution and an organic solvent are not chemicallycompatible.

There are two basic techniques that can be used to make a thermosetproduct described herein: a one-shot technique, and a prepolymertechnique. In each technique, the combining of first and second reactivecomponents results in a thermoset product with a viscosity thatincreases as reactants in the first and second reactive componentsreact. The viscosity passes through a value that is low enough for thethermoset product to be extruded out of the mixing chamber and throughan extrusion nozzle, and high enough for the thermoset product to have apredetermined layer resolution that is conducive for use in making a 3Dobject having a predetermined shape resolution.

In one embodiment, the prepolymer technique involves a first reactionbetween a composition including isocyanate and a composition including apolyol and/or polyamine mixture to produce a prepolymer. As used herein,a “prepolymer” includes, but is not limited to, a urethane and/orurea-containing polymer polymer that results by reacting either polyoland/or polyamine mixture with an excess of isocyanate, or isocyanatewith an excess of polyol and/or polyamine mixture. A prepolymer thatresults from reacting polyol and/or polyamine mixture with an excess ofisocyanate is referred to herein as an “isocyanate prepolymer.” Aprepolymer that results from reacting isocyanate with an excess ofpolyol and/or polyamine mixture is referred to herein as a “polyoland/or polyamine prepolymer.” More than one type of polyol can be used,more than one type of polyamine can be used, and more than one type ofisocyanate can be used. In one embodiment, a composition that includesan isocyanate prepolymer can be supplemented with additional isocyanate.The additional isocyanate can be the same isocyanate used to make theisocyanate prepolymer, a different isocyanate, or a combination thereof.In one embodiment, a composition that includes a polyol and/or polyamineprepolymer can be supplemented with additional polyol and/or polyamineprepolymer. The additional polyol and/or polyamine prepolymer can be thesame polyol and/or polyamine prepolymer used to make the polyol and/orpolyamine prepolymer, a different polyol and/or polyamine prepolymer, ora combination thereof.

The prepolymer differs from the product of the one-shot techniquebecause the prepolymer does not cure into a completely reacted product.In one embodiment, an isocyanate prepolymer has less than 20%, less than14%, less than 11%, or less than 8.5% unreacted isocyanate groups. Inone embodiment, an isocyanate prepolymer has greater than 0.1%, greaterthan 0.5%, greater than 1%, greater than 2.5%, greater than 5%, orgreater than 7% unreacted isocyanate groups. In one embodiment, anisocyanate prepolymer has from 0.5% to 5%, from 2.5% to 8%, or from 5.0%to 8.0% unreacted isocyanate groups. In one embodiment, a polyol and/orpolyamine prepolymer has less than 14%, less than 11%, or less than 8.5%unreacted alcohol and/or amine groups. In one embodiment, a polyoland/or polyamine prepolymer has greater 1%, greater than 2.5%, greaterthan 5%, or greater than 7% unreacted alcohol and/or amine groups.

The prepolymer technique also involves a second reaction between theprepolymer (e.g., the first reactive component) and a polyol and/orpolyamine mixture (e.g., the second reactive component). The first andsecond reactive components are introduced into a mixing chamber for aperiod of time sufficient to form a partially reacted thermoset productand result in the predetermined layer resolution upon exiting the mixingchamber, and extruding the partially reacted thermoset product out ofthe mixing chamber through an extrusion nozzle and onto a substrate. Theviscosities of the first and second reactive components are typicallyclose enough that a mixing chamber with a static mixer results insufficient mixing of the two reactive components. Examples of staticmixers include 12 fold and 24 fold mixers, blade mixers, and helicalmixers. For example, a static mixer can be used when the viscosity ofthe first reactive component and the viscosity of the second componentare within a factor of no greater than 10, no greater than 6, or nogreater than 3 of each other. In another embodiment, the viscosities ofthe two reactive components are different enough to require use of amixing chamber with an agitator, such as a mechanical agitator or a highpressure impingement mixer. Other non-static mixers include an emulsivemixer, a simple agitated chamber, or a dispersive mixer.

Optionally and preferably, the reaction to produce a thermoset productdescribed herein includes other additives, including but not limited to,a catalyst, a chain extender, a curing agent, a surfactant, a pigment, adye, a rheology modifier, and a filler such as an inorganic filler.Examples of inorganic fillers include, but are not limited to, siliconoxide, a ceramic pre-cursor, or glass. An additive can be present in thefirst or second reactive component, or can be separately added to themixing chamber as the first and second reactive components are beingadded to the mixing chamber. One or more than one additive can bepresent (e.g., a catalyst and a chain extender), and more than one typeof additive can be present (e.g., a reaction can include dyes, multiplecatalysts, multiple chain extenders, rheology modifiers, etc.). In oneembodiment, a rheology modifier can alter thixotropic characteristics ofa partially reacted thermoset product, and in one embodiment, a rheologymodifier does not alter thixotropic characteristics of a partiallyreacted thermoset product. In one embodiment, a partially reactedthermoset product is not thixotropic, e.g., the partially reactedthermoset product does not decrease in viscosity when exposed to a forcesuch as shaking, agitation, shearing, and the like. In one embodiment, a3D object described herein does not have a thixotropic characteristic.

A catalyst is a compound that increases the rate of a chemical reaction.In one embodiment, a catalyst does not undergo any permanent chemicalchange. In another embodiment, a catalyst increases the rate of achemical reaction and reacts with one or more reactive component. Forinstance, a catalyst can include hydroxyl, amine, and/or isocyanatefunctionality.

Chain extenders include low molecular weight highly reactive diols anddiamines. In some embodiments, they are designed to form hard segmentsof two or more urea/urethane linkages between isocyanates. Molecularweights can range from, for instance, 18 to 1,000, in some embodimentswith primary hydroxyl or amine termination. Examples include water,butanediol, di-ethylene glycol, hexane diol, E-100, E-300.

In one embodiment, the additive is water. The use of water as anadditive in the production of a urethane and/or urea-containing polymerthermoset product results in a polyurethane/polyurea foam.

The completely reacted thermoset product of a 3D object produced usingthe methods described herein has several characteristics, including, butnot limited to hardness, resilience, strength, elasticity, density,durability, abrasion resistance, and flexibility.

Hardness refers to the amount of pressure that needs to be applied todeform the completely reacted thermoset product a certain distance. Inone embodiment, a completely reacted thermoset product has a Shore Ahardness from 20 to 120. For instance, the hardness can have a minimalShore A value of at least 20, at least 30, at least 40, at least 50, atleast 60, at least 70, at least 80, at least 90, at least 100, at least110, or at least 120, and a maximum Shore A value of no greater than120, no greater than 110, no greater than 100, no greater than 90, nogreater than 80, no greater than 70, no greater than 60, no greater than50, no greater than 40, no greater than 30, or no greater than 20. Inanother embodiment, a completely reacted thermoset product has a Shore Dhardness from 3- to 120. For instance, the hardness can have a minimalShore D value of at least 30, at least 40, at least 50, or at least 60and a maximum Shore D value of no greater than 120, no greater than 110,no greater than 90, no greater than 80, or no greater than 70. Hardnessis measured using a durometer, such as an ASTM D2240 durometer. Whilethe hardness of non-foams can be measured using the Shore hardnessscale, foams are typically too soft for the Shore hardness scale. Unitsof hardness for foams are Indentation Force Deflection (IFD), and thestandard is set out by the Polyurethane Foam Association (Joint IndustryFoam Standards and Guidelines, Section 4.0, available on the world wideweb at www.pfa.org/jifsg/jifsgs4.html), the amount of force, in pounds,required to indent a 50 sq in foot 25% of its thickness, referred to as25% IFD. In one embodiment, a completely reacted foam thermoset producthas a 25% IFD from at least 15 lbs, at least 20 lbs, at least 30 lbs, orat least 35 lbs, to no greater than 60 lbs., no greater than 50 lbs., orno greater than 40 lbs. More rigid foams can also be characterized bycompression resistance of 10% deflection, as defined in ASTM D1621, oraccording to bending strength as defined in EN 12089. In one embodiment,a rigid foam has a compression resistance ranging from 25 to 200 kPa, ora bending strength between 150 kPa and 2000 kPa.

Density refers to the mass of a completely reacted thermoset product perunit volume. In one embodiment, density is the mass of a completelyreacted product excluding any filler. In one embodiment, a completelyreacted solid thermoset product has a density of at least 0.8 g/mL, orat least 0.9 g/mL, and no greater that 1.3 g/mL or no greater than 1g/ml. In one embodiment, a completely reacted foam thermoset product hasa density of at least 0.05 g/ml, at least 0.1 g/ml, at least 0.5 g/ml,or at least 0.75 g/ml, and no greater than 1 g/ml, or no greater than0.9 g/ml.

Density is found by measuring mass on a material that has a definedgeometry and size. Durability refers to the ability for a part tosustain repeated stresses without failing. Durability can be measuredtwo ways. In one embodiment, a stress-strain test can be performed inaccordance with ASTM D638. Briefly, the part can be pulled at a constantstrain rate, and the stress at the point at which the part breaksentirely (i.e., one side of the part is detached from the other) ismeasured. This can be measured when the force is applied in the printdirection and transverse to the print direction. If the stress at breakis significantly lower in the print direction (less than 75%), then thepart is significantly less durable than a part that is fabricated byanother means (i.e. injection molded) would be. Using this test acompletely reacted thermoset product described herein has a durabilityof stress at break in the print direction of at least 50%, at least 55%,at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, orat least 85%. In another embodiment, flexural durability is measured inaccordance with ASTM D813 or ASTM D430. Briefly, in this method the testspecimen is pierced or cracked and then repeatedly bent or stretched.The test measures the increase in size in the hole or the number ofcycles required to get to a certain crack size. In parts that are 3Dprinted, the durability of the part is analyzed when the deformation isin varied directions relative to the print direction. The durability ofthe part is determined by the weakest direction (i.e., the directionwhere failure occurred at the lowest number of repeated deformation). Asa 3D printing methodology, this disclosure uses a new hardeningmechanism as the part is formed: rather than relying on photo-curing ofacrylates or cooling to harden, this disclosure carefully times thechemical cure rate of a thermoset. With respect to polyurethanes,polyureas, and polyurethane/polyureas, such a strategy takes fulladvantage of the mechanical strength of polyurethane thermosetelastomers, which can be superior to photo-cured acrylates orthermoplastic urethanes (TPUs). One innovation to be employed is thespecific design and synthesis of urethane precursors, urea precursors,and urethane/urea precursors (prepolymers, such as isocyanate oligomers)and formulation ingredients such as chain extenders, curing agents, andcatalysts, to meet the demands for print resolution and z-direction partstrength in 3D printing. Durability of FFF fabrication methods arelimited by the incorporation of voids between strands during theprinting process, with porosity as high as 5-15% range. The methodsdescribed herein can facilitate the selection of printing parameters toattain lower porosities such as no greater than 1%.

In one embodiment, a multi-ingredient (e.g., a 3-ingredient,4-ingredient, a 5-ingredient, 6-ingredient, 7-ingredient, or8-ingredient) urethane elastomer system is used. For instance, 3 or morereactive components can be used to produce a partially reacted thermosetproduct. In one embodiment, the resulting 3D object can have one or moreproperties vary between different areas of the 3D object. In oneembodiment, the urethane system can print parts that cure to have aShore A hardness from 30 to 80. A significant advantage of this systemover photo-cured urethane-acrylate or acrylate-rubber systems availableon the market is the durability of the parts. Urethane systems are thematerial of choice for elastomers requiring toughness, abrasionresistance, and low hysteresis, particularly in automotive parts, shoesoles, and prosthetics. Mechanical durability is a property that ishelpful to move 3D printing from the domain of prototype development tomanufacturing of functional parts. Ratios of reactive components can becontrolled to achieved desired stoichiometric ratios. Accordingly,software can be used that controls the relative ratios of reactivecomponents to be utilized in order to achieve, for instance, desiredcure profiles, material properties, desired resolution, and processingwindow (U.S. Provisional Application No. 62/595,400, “Three-DimensionalPrinting Control”).

In one embodiment, the technology used herein uses a 3D printer whichhandles delivery of reactive systems (e.g., a first reactive componentand a second reactive component). The process of manufacturing the partsuses one or more of the initial viscosities of the reactive components,the viscosity of the mixture exiting the extrusion nozzle, cure rateprofiles, and interlayer adhesion (e.g., cross-linking) to determineextrusion amounts, setting times before an additional layer is applied,and so on. Compared to thermoplastic FFF, this product demonstratesadvantages with regards to durability, z-direction strength, andporosity.

In the practice of this disclosure, the reactive system has a cureprofile that matches the capabilities of the specific printer employedas well as demands for part resolution. A printable partially reactedthermoset product will have value propositions (e.g., characteristics),such as interlayer adhesion and part durability, that will be inherentto the urethane.

Thermoset compositions are chosen such that the reactive components havea viscosity after mixing to maintain part resolution and inhibit layerbreak-up, e.g., the process by which a liquid stream breaks intodroplets. This process is governed by surface tension, and the methodsdescribed herein can prevent this phenomenon by slowing the process witha high viscosity, and then solidifying faster than the droplet formationprocess. The printer includes a mixing chamber or zone designed suchthat the reactive components are intimately mixed, and with a residencetime and optional catalyst level such that the reaction mixture has therequired viscosity upon exiting the mixing zone through an extrusionnozzle. The thermoset compositions are chosen such that resolution isachieved but also such that the reaction is not complete when the nextlayer is deposited, e.g., when the next layer is deposited on apartially reacted thermoset product. In addition, the cure rate of thepartially reacted thermoset product is balanced so that it is slowenough that it doesn't clog in the mixer, fast enough that the viscosityis sufficient to inhibit free flow of the part and reduce resolution,and still slow enough in late cure that the next layer will bond. Thus,this disclosure includes balancing cure rate with flow rate andcorresponding residence times in a mixer at the printhead. Likewise, inthis disclosure the matching viscosities and compatibilities of the tworeactive components that will be mixed by adjusting compositions, e.g.,viscosities and/or compatibilities can be matched by, for instance, (i)adjusting a ratio of monomeric isocyanate:isocyanate prepolymer in onereactive component, and by adjusting a ratio of polyol and/or polyaminemixture:polyol and/or polyamine prepolymer in the other reactivecomponent, or (ii) adjusting the initial viscosity/molecular weight ofthe prepolymer as synthesized to match viscosites. The mixing chambercan include static mixing, or mechanical agitation can be used ifneeded. Also, when materials from finite product set are blended, theycan they be blended in such a way that does not sacrifice materialdurability or cure control.

In any section of the extrusion device where the two reactive componentsare mixed, clogging can occur. The inventor has observed clogging in twoscenarios: 1) gradual buildup of cured material in the mixer due to acombination of insufficient flow rate, fast cure rate, and/or a largedistribution of residence times in the mixer, and/or 2) viscositymismatch and chemical incompatibility between the two components,leading to channeling flow of the low viscosity material past the highviscosity material in the mixer. Furthermore, when flow through themixer is stopped or started, the mixer can be filled with adisproportionate amount of one component if the viscosities are notsimilar or controls are not instituted to control the flow of onecomponent separate from the first. Accordingly, in one embodiment thereactive components that are combined to form a mixture have viscositiesthat are different from each other by no greater than a factor of 3. Forinstance, the reactive components have viscosities that differ by aratio of 1 to no greater than 3 (e.g., 1:3), 1 to no greater than 2(e.g., 1:2), or 1 to no greater than 1 (e.g., 1:1).

In one embodiment, the reactive components have a flow rate through themixing chamber such that the flow rate of the partially reactedthermoset product is constant at constant pumping pressure and/or loadfor at least 10 minutes or at least 20 minutes. In one embodiment, thereactive components have a flow rate through the mixer such that theflow rate of the partially reacted thermoset product is reduced by nogreater than 5% (at least 95% of initial flow rate), no greater than10%, no greater than 15%, or no greater than 20% at constant pumpingpressure and/or load for at least 10 minutes or at least 20 minutes. Inone embodiment, the partially reacted thermoset product does not formclogs in the mixing chamber and/or the extrusion nozzle when flow stopsfor no greater than 5 seconds, no greater than 10 seconds, or no greaterthan 30 seconds. In one embodiment, the partially reacted thermosetproduct does not increase pressure and/or load present in the mixingchamber by more than 10%, more than 15%, more than 20%, or more than 25%from the starting pressure in no greater than 2 minutes, no greater than5 minutes, no greater than 10 minutes, or no greater than 60 minutes.Maintaining a flow through the mixing chamber, an absence of clogs, or aminimal increase in pressure and/or load can occur when the amounts offirst and second reactive components are constant or are changing.

As used herein a “processing window” refers to the range of flow ratesfor a partially reacted thermoset product through a mixing chamber andextrusion nozzle. The lowest flow rate of a processing window is theslowest flow rate that can be maintained that does not increase pressureand/or load present in the mixing chamber by more than 10%, more than15%, more than 20%, or more than 25% from the starting pressure in nogreater than 2 minutes, no greater than 5 minutes, no greater than 10minutes, or no greater than 60 minutes. The highest flow rate of aprocessing window is the fastest flow rate that can be maintainedwithout exceeding the pressure limitations of the printing system, e.g.,limitations of the mixing chamber, the pumping system, etc. Printersequipped with capabilities to impart higher pressures to move the fluidswill have larger processing windows. Similarly, partially reactedthermoset products that have a slow growth or plateau in viscosity willhave a larger processing window. Large processing windows areadvantageous for minimizing interruptions due to clogs, speeding printtimes, and allowing operation with a range of nozzle diameters andresolutions. In view of the teachings of the present disclosure, theskilled person can determine the processing window for a set of reactivecomponents, and alter variables including the types and concentrationsof chemicals in reactive components to achieve useful processingwindows. In one embodiment, a useful processing window is one where theratio of the highest flow rate to the lowest flow rate is at least 2, atleast 10, at least 25, at least 50, at least 75, at least 100.

An advantage of the methods described herein is that flow rate throughthe nozzle can give a way to control resolution. With a shorterresidence time, or faster flow rate, the partially cured thermosetproduct will typically have reduced resolution. It can be desirable toshorten overall printing times, and shorter overall printing times canbe achieved by moving slowly in areas of the part requiring highresolution, but flowing more quickly in areas of the part that do notrequire high resolution, such as filling an outlined shape.

This disclosure further encompasses extruder designs wherein the mixingzone is easily replaced. The disclosure further encompasses cleaningmethods wherein any clogs of crosslinked material are removed.

A curing thermoset product described herein is deposited as a layer orstrand when the diffusion rate of molecules from one layer into anotherlayer is substantially higher, optionally including low molecular weightcomponent curing agents having diffusion rates that are much faster.Furthermore, the density of reactive groups is typically 2-20% byweight, where the density of reactive groups is given as moles ofisocyanate or moles of hydroxyl per unit volume as derived from measuredNCO or hydroxyl content. % NCO is a standard measurement, and is wt % ofNCO functionalities per weight of the formula. Not only is the diffusionrate high, but the opportunity to establish covalent bonds between thelayers is substantial. This disclosure permits the flexibility to adjustthe density of reaction groups, their reactivity, and their mobility sothat strong interlayer adhesion can be achieved, approaching strengthscomparable to bulk mechanical properties. Typically, a second layer isdeposited on a first layer while the first layer is partially reacted,thereby increasing the interlayer adhesion between the two layers. Inone embodiment, the time that can elapse between depositing each layercan be no greater than 0.5 minute, no greater than 1 minute, no greaterthan 1.5 minutes, no greater than 2 minutes, no greater than 5 minutes,or no greater than 10 minutes. Application of energy, such as heat, cansimultaneously speed diffusion and reaction rates. Accordingly, in oneembodiment the method includes application of spot or ambient heating atthe top layer to simultaneously promote bonding between layers and speedthe hardening process.

While not wishing to be bound by theory, it is further postulated thatamorphous thermoplastic FFF interfacial strength of existingtechnologies is hindered by the incorporation of small voids or poresbetween strands, typically from 45 to 15% (Paul—“Eliminating Voids inFDM Processed Polyphenylsulfone, Polycarbonate, and ULTEM 9085 by HotIsostatic Pressing”, Mary Elizabeth Parker, Research report 2009, SouthDakota School of Mines and Technology). These voids exist because thematerial viscosity is too high to flow and fill the gaps betweenstrands, and leads to mechanical weakness in the printed parts. Thepartially reacted thermoset product described herein can have aviscosity that is several orders of magnitude lower than the amorphouspolymer of existing FFF methods, and therefore can easily flow the shortdistance required to fill voids between strands and eliminate gaps.

In one embodiment of the reactive system described herein, the parthardness is a kinetic function of the extent of cure. The initial curingcomponent (e.g., the partially reacted thermoset product) is very lowviscosity, and the hardness develops as the curing reaction continues.Thus, for a large part, the portions of the part that are printed firstare the stiffest, and thus can support weight, while the fresh layersare still soft and able to cure and adhere to subsequent layers.Furthermore, the rate of cure can be adjusted significantly by adjustingthe formula reactivity (e.g., the density of reactive groups) and thecatalyst levels in order to accommodate larger part designs and prints.The thermoset 3D print system described herein therefore de-couples partsize and warpage from the requirements for strong interlayer adhesion.

It has been found that FFF part resolution and surface roughness ofexisting methods is directly related to the viscosity of the materialwhen it is extruded. PLA, which is a favorite in 3D printing because ofits high resolution, has very low viscosity and minimal nonlinearviscoelasticity and die swell. The low viscosity of the partiallyreacted thermoset product described herein permits the use of lowerdiameter nozzles. For a given pressure and die length, the volumetricflow rate varies as R⁴/η, where R is the nozzle radius and η is theviscosity of a simple fluid; significant drops in viscosity cantherefore lead to drops in nozzle radius without sacrificing printingspeeds.

Prior to cure, and at room temperature, the methods described herein canresult in partially reacted thermoset products having viscosities as lowas 1000 cP, without die swell. With viscosities 100-10,000 times lowerthan the viscosities of typical amorphous polymers, the nozzle radiusused in the methods described herein can decrease by a factor of 3 to10, enabling significantly higher print resolution without changingprint speed. Alternatively, ETP printing speed can increase severalorders of magnitude without hurting part resolution. ETP printing speedmay be slowed by other factors, such as hardening rates of the materialand robot head speed, and the skilled person will recognize that theseparameters can be controlled and engineered separately.

The shape and size of the tip of the nozzle is not intended to belimiting, because it is expected that nearly any size and shape can beused with the partially reacted thermoset product. The skilled personwill recognize that as the size of the nozzle tip decreases, theviscosity of the partially reacted thermoset product being extrudedshould be increased to compensate for interfacial tension that can breakup the strand as it exits the nozzle tip. The skilled person will alsorecognize that as the size of the nozzle tip increases, the viscosity ofthe partially reacted thermoset product being extruded should beincreased to compensate for the weight of the strand being extruded. Alarger strand has a greater tendency to spread.

The thermosets described herein can be cured at mild temperatures, andeven room temperature, negating the need for careful thermal control.Thermosets are seldom cured at temperatures above 50° C. These mildtemperatures not only enable broad material property versatility withinthe part and reduced printer cost and design, but can also allow theincorporation of more thermally sensitive components, such aselectronics and sensors, during the printing of the part. Furthermore, athermoset product, such as urethane materials, may be 3D printed uponother metal or plastic parts (including, but not limited to, 3D printedparts) at low temperatures, without inducing thermal warpage ordegradation. Accordingly, a 3D object described herein can include morethan one type of material. In some embodiments, such as embodiments thatuse a semi-crystalline polyol (e.g., a polyester polyol), thetemperature of the mixing chamber can be elevated above the meltingpoint of the semi-crystalline polyol and then extruded and depositedonto a substrate and exposed to a temperature below the melting point ofthe semi-crystalline polyol. The subsequent crystallization aids inmaintaining the shape of the 3D object while other components of thethermoset cure.

Existing photo-cured acrylate printer systems, such as the 3DS ProJetand the Stratasys Polyjet printers, operate by depositing liquiddroplets of acrylates which are subsequently cured by light. By varyingthe acrylate reactive group density within each droplet, the materialproperties can be varied at a pixel level. The application of a curingliquid enables strong interlayer adhesion, largely eliminating thestrength anisotropy observed in FFF. A disadvantage of these systems isthe inkjetting layer thickness and the requisite inkjet printer headsize; these attributes limit the scalability and part size for thephoto-cured systems. The technology described herein offers similarbenefits as the photo-cured systems over FFF of amorphous polymers(strong interlayer adhesion and voxel-level control of materialproperties). Printing with the thermosets described herein offersenhanced part durability, reduced printer costs, and increased partsize.

With respect to foams, numerous applications are envisioned, includingorthotics, prosthetics, footware, grips, seals, gaskets, sound barriers,shock absorption, prosthetic joints, among many others. Products withvaried foam properties can be particularly advantageous. For example,informed by pressure-mapping, mattresses can be fabricated to provideideal support for an individual's weight distribution and preferredsleeping position. Vibration dampening foams can be designed with variedcellular structure and material elasticity to dampen a broad spectrum ofvibrations with a minimum amount of material. Space-efficient seatingcan be built for furnishings or transportation. Energy absorbing safetyhelmets can be designed with a higher level of comfort and fit. Foampadding can be designed for medical applications (such as wheel chairseating) with conforming fit and reduced pressure points to reduce theincidence of pressure-induced skin ulcers. Areas with open-cellstructures can be placed within a structure of closed-cell structures topreferentially channel the flow of air of liquids through the part.

While the following description is in the context of foams, thedescription applies to thermoset products, including urethane and/orurea-containing polymers in general, both non-foam and foam. Foams areavailable in a range of hardness and resiliencies. The urethane and/orurea-containing polymer is very durable, permitting the foam to be usedrepeatedly without a change in properties. This range of propertiespermits these materials to be used in clinical settings where rigidpositioning is required or where pressure distribution is moredesirable.

Foams of urethane and/or urea-containing polymers are the product of areaction between two reactant components. The range of foam propertiesis achieved by altering the relative weights of formulation componentsin order to balance reaction speed, interfacial tension of the reactingmixture, and elasticity of the polymeric scaffold. In 3D printing, anextrusion nozzle deposits material, e.g., partially reacted thermosetproduct, on a substrate layer by layer, following a 3D computer model ofthe desired 3D object.

The novel foam precursor formulas described herein enable highresolution 3D deposition to form a custom 3D foam object. By partiallyadvancing the reaction of the precursors, such as polyurethaneprecursors, and adjusting catalyst and surfactant levels, it is possibleto deposit the partially reacted thermoset product while maintaining thedesired predetermined part resolution and mechanical integrity of thefoam.

The production of a foam of urethane and/or urea-containing polymersdiffers from the production of a non-foam urethane and/orurea-containing polymer by the inclusion of water. Foams of urethaneand/or urea-containing polymer are formed by the simultaneous reactionof isocyanates with water to form urea linkages and produce gas, and thereaction of isocyanates with multifunctional high molecular weightalcohols to form a crosslinked elastomeric foam scaffold. The reactionchemistry is illustrated here.

Urea/Gas Evolution Reaction

—NCO+H₂O→—NH₂+CO₂(g)

isocyanate amine

—NCO+—NH₂—NH—CO—NH—

isocyanate+amine urea

Urethane/Polymerization Reaction

—NCO+—OH→—NH—COO

isocyanate+alcohol urethane

The gas evolution forms the porous structure of the foam, whilesurfactant addition stabilizes the foam structure to maintain a finecellular structure. The concentrations of catalysts for each reaction,combined with the alcohol reactivity, balance the relative reactionrates so that sufficient polymer weight is built during the gasevolution to form a mechanically stable foam structure. In view of theteachings of the present disclosure, the skilled person can balancethese variables, for instance by the inclusion of a blowing agent, toform a mechanically stable foam structure.

The conventional precursors used to make a foam of urethane and/orurea-containing polymers are low viscosity liquids. In typical foamingsystems, the reacting liquid mixture is injected into a mold or foamingchamber, and the low viscosity of the liquid allows the mixture to flowand completely fill the mold while it expands. In 3D printing, the lowviscosity and flow is undesirable; if the liquid spreads as it isdeposited on the platform, the process produces a reacting puddle withlittle or no form.

While the reacting mixture starts as a liquid, as the polymerizationreaction advances, the viscosity of the mixture increases until itultimately forms a solid, crosslinked network. Before the crosslinkednetwork is formed, the reacting mixture passes through a viscosity thatis high enough for high resolution printing. Therefore, the innovationincludes precursors and their respective formulas such that the reactingmixture starts at a printable viscosity, and stays at that viscositylong enough to have sufficient working time (e.g., processing window)that the system is robust (FIG. 1). In one embodiment, an excess ofisocyanates is pre-reacted with a polyol and/or polyamine mixture toachieve a printable starting viscosity. One of skill in the art can usetechniques that are often used in the polyurethane and polyurea industryto reformulate the reactive components and control the speed of gasevolution and the stability of the foam structure.

In one embodiment, foams are formed by reacting simple monomers: adi-isocyanate, water, and multi-functional alcohol, also referred toherein as a polyol, or a multi-functional amine. The quantity of waterin the formula affects the foam density, and also the strength of thefoam scaffold. The molecular weight of the polyol and/or polyaminemixture determines the crosslink density of the foam scaffold and theresulting elasticity, resiliency, and hardness of the foam. A nearlystoichiometric quantity of di-isocyanate is used in order to fully reactwith the water and a polyol and/or polyamine mixture.

Prepolymer synthesis is a technique commonly used to alter the cureprofile of a polyurethane or polyurea system. In prepolymer synthesis, astoichiometric excess of di-isocyanate is reacted with a polyol and/orpolyamine mixture. The resulting prepolymer has a higher molecularweight than the starting di-isocyanate, though molecules in thepre-polymer have isocyanate functionality and therefore are stillreactive. Because of the higher molecular weight, hydrogen bonding,and/or urea linkages, the prepolymer also has a higher viscosity. Thisprepolymer can be subsequently reacted with a polyol and/or polyaminemixture and water to produce a foam with substantially the same foamscaffold composition that is achievable without prepolymer synthesis.However, viscosity growth profile is altered, typically starting higher,and increasing more slowly, and therefore the morphological features ofthe foam such as foam cell size and cell stability, can result in a foamwith a very different appearance. Foams which start as prepolymersrather than their starting monomer components are common: householdspray insulation foams, steering wheels, and microcellular shoe solesare examples.

For precursor design, isocyanate and polyol and/or polyamine mixturecomponents which are commonly employed for cushioning or insulatingfoams can be used to systematically design prepolymers suitable for highresolution 3D printing. The curing profile of the system can be adjustedby tuning the ratios of the urea and urethane reaction catalysts inorder to broaden the time window that the material is at a printableviscosity to, for instance, at least 30 seconds, and achieve a stablefoam cellular structure. In one embodiment, a formulation maintainsprintable viscosity for at least 30 seconds, and a foam density of atmost 0.5 g/cm3.

The composition is used in a 3D printer systems such as manufactured byHyrel 3D (Norcross, Ga.), and in one embodiment the formula is chosen toform a printed foam object.

Once the formula is adequately mixed, the water reaction, which producesgas, is the fastest reaction and the liquid will start to froth andexpand. Ultimately, the volume of the liquid increases, for instance 10to 30 times, to form standard foam densities. If this expansion startsin the mixing zone of the extruder, the froth may emerge from theextruder at a fast, difficult-to-control rate. In this case, the skilledperson will recognize that a shorter mixing zone can be used, or anarrower extrusion tip used to provide additional back pressure,therefore keeping the gas dissolved. Once the froth is deposited on theplatform, the liquid will continue to expand. The skilled person willrecognize that expansion takes place during the time required to print asingle layer, and will adapt the robot controls to accommodate printingat the corresponding higher point.

A challenge frequently encountered in 3D printing is the adhesion of theprinted layers. Interlayer adhesion of one layer with the next is usefulin making an object with strength and integrity in the verticaldirection. Interlayer adhesion with the foaming system described hereinis significantly improved over the existing amorphous polymer systems,as the slow urethane reaction is responsible for adhesive properties insome of the strongest industrial glues. Because the lower layer is notcompletely cured when the next layer is deposited, reactive chemicalfunctionalities will be available from the lower layer to react with thenext layer, and form strong covalent bonds between the layers. In oneembodiment, to achieve sufficient interlayer adhesion, the speed toprint a single layer is increased, first by increasing the depositionrate, and next by reducing the part dimensions. In another embodiment,the urethane reaction is decreased by adapting the precursor formula byreducing the urethane reaction catalyst level, increasing the amount ofcomponents in a polyol and/or polyamine mixture with slower-reacting,secondary hydroxyl groups, or both. Interlayer adhesion is measuredfirst by manipulation on the final cured object, and validated bymulti-directional tensile testing to confirm that the vertical directionstrength is at least 50% of the strength of the part in the otherdirections.

Support foams are not a single density, hardness, or resilience, but canspan a wide range of performance. This disclosure extends the foamproperty range of the formula and foam that was developed. Foam densityand hardness are interrelated: low density foams are often softer foams.A range of foam density and hardness can be achieved first by varyingthe level of blowing agent such as water in the formulation and byadjusting the extent of excess isocyanate in the formula. Increasing thedegree of functionality of the components of the polyol and/or polyaminemixture (e.g., incorporating some 4- or 6-functional polyols) increaseshardness, and also increases the viscosity growth rate during cure. Foamresilience can be altered by varying the polyols and/or polyaminesincorporated in the formula. Memory foams can be achieved by reducingthe molecular weight of the polyols and polyamines; high resiliency canbe achieved by incorporating graft polyols. In one embodiment, the foamdensity range is less than 0.3 g/cm3, ranging from 30-50 ILFD hardness,and resilience ranging from 10 to 50%. Foam properties also include opencell content and closed cell content. Open cell foams are defined ascellular structures built from struts, with windows in the cell wallswhich can permit flow of air or liquid between cells. Closed cells areadvantageous for preventing air flow, such as in insulationapplications.

The computer in the system of the present disclosure has two basicfunctions. The first is to help the operator design the 3D object in away that it can be made. The second is to translate the design intocommands to control the robotic motion of the extruder tip, and todeliver these commands in a way so that the object is formed. In someapplications, the object design will exist, and the only function of thecomputer will be to deliver the appropriate commands. The computer mayalso control the relative ratios of the reactive components in order tocontrol the foam density and mechanical properties throughout the part.A 3D object produced using the methods described herein includesmultiple layers. In one embodiment, the number of layers is at least 3,at least 5, at least 10, at least 20, at least 50, or at least 100.

A computer controlled pump or pumps may be used to force reactivecomponents through the mixing chamber and out of the extrusion nozzle.Likewise, appropriate level detection system and feedback networks, wellknown in the art, can be used to drive a fluid pump or a liquiddisplacement device to maintain reactive component volumes in thecontainers.

In addition, there may be additional containers used in the practice ofthe disclosure, each container having a different type of component,catalyst, water, pigments, and so on that can be selected by the systemand added to the first or second reactive component before they arecombined in the mixing chamber, or added to the mixing chamberseparately. In this regard, the various materials might provide plasticsof different colors, or have both insulating and conducting materialavailable for the various layers of electronic products.

The present disclosure satisfies a long existing need in the art for aCAD and CAM system capable of rapidly, reliably, accurately andeconomically designing and fabricating three-dimensional plastic partsand the like from thermoset starting materials (U.S. ProvisionalApplication No. 62/595,400, “Three-Dimensional Printing Control”).

Further modifications and alternative embodiments of this disclosurewill be apparent to those skilled in the art in view of thisdescription. It will be recognized, therefore, that the presentdisclosure is not limited by these example arrangements. Accordingly,this description is to be construed as illustrative only and is for thepurpose of teaching those skilled in the art the manner of carrying outthe disclosure. It is to be understood that the forms of the disclosureherein shown and described are to be taken as the presently preferredembodiments. Various changes may be made in the implementations andarchitectures. For example, equivalent elements may be substituted forthose illustrated and described herein, and certain features of thedisclosure may be utilized independently of the use of other features,all as would be apparent to one skilled in the art after having thebenefit of this description of the disclosure.

EXEMPLARY EMBODIMENTS Embodiment 1

A method of creating a three dimensional (3D) object from reactivecomponents that form a thermoset product using extruded thermosetprinting, comprising:

-   -   providing first and second reactive components that are        effective to form a thermoset product having a predetermined        layer resolution during the method;    -   introducing the first and second reactive components into a        mixing chamber where mixing occurs to form a mixture,        -   wherein the first and second reactive components have a            residence time in the mixing chamber effective to form a            partially reacted thermoset product in the mixing chamber            and result in the predetermined layer resolution upon            exiting the mixing chamber, and        -   wherein the first and second reactive components have a            residence time in the mixing chamber insufficient to            completely react;    -   extruding the partially reacted thermoset product out of the        mixing chamber through an extrusion nozzle and onto a substrate;    -   moving the extrusion nozzle and/or the substrate to form a 3D        object having a predetermined shape resolution.

Embodiment 2

The method of Embodiment 1 wherein the thermoset product comprises aurethane and/or urea-containing polymer.

Embodiment 3

The method of Embodiment 1 or 2

-   -   wherein the first reactive component comprises an isocyanate,    -   wherein the second reactive component comprises a polyol        comprising at least one terminal hydroxyl group, a polyamine        comprising at least one amine that comprises an isocyanate        reactive hydrogen, or a combination of the polyol and the        polyamine.

Embodiment 4

The method of any one of Embodiments 1-3 wherein the isocyanatecomprises R—(N═C═O)_(n), where n is at least 2.

Embodiment 5

The method of any one of Embodiments 1-4 wherein the isocyanate is adi-isocyanate (R—(N═C═O)₂).

Embodiment 6

The method of any one of Embodiments 1-5 wherein the R comprises analiphatic group, a cyclic group or a combination thereof.

Embodiment 7

The method of any one of Embodiments 1-6 wherein the cyclic groupcomprises methylene diphenyl diisocyanate (MDI) or toluene diisocyanate(TDI).

Embodiment 8

The method of any one of Embodiments 1-7 wherein the MDI comprisesmonomeric MDI, polymeric MDI, or an isomer thereof.

Embodiment 9

The method of any one of Embodiments 1-8 wherein the isomer comprisesthe chemical formula C₁₅H₁₀N₂O₂.

Embodiment 10

The method of any one of Embodiments 1-9 wherein the isomer is 2,2′-MDI,2,4′-MDI, 4,4′-MDI, or a combination thereof.

Embodiment 11

The method of any one of Embodiments 1-10 wherein the TDI is an isomerof TDI comprising the chemical formula C₉H₆N₂O₂.

Embodiment 12

The method of any one of Embodiments 1-11 wherein the isomer comprises2,4-TDI, 2,6-TDI, or a combination thereof.

Embodiment 13

The method of any one of Embodiments 1-12 wherein the aliphatic groupcomprises a monomeric di-isocyanate, a blocked polyisocyanate, or acombination thereof.

Embodiment 14

The method of any one of Embodiments 1-13 wherein the monomericdi-isocyanate comprises hexamethylene diisocyanate (HDI), methylenedicyclohexyl diisocyanate, hydrogenated MDI (HMDI), isophoronediisocyanate (IPDI), or a combination thereof.

Embodiment 15

The method of any one of Embodiments 1-14 wherein the HDI compriseshexamethylene-1,6-diisocyanate.

Embodiment 16

The method of any one of Embodiments 1-15 wherein the HMDI comprisesdicyclohexylmethane-4,4′diisocyanate.

Embodiment 17

The method of any one of Embodiments 1-16 wherein the blockedpolyisocyanates comprise HDI trimer, HDI biuret, HDI uretdione, IPDItrimer, or a combination thereof.

Embodiment 18

The method of any one of Embodiments 1-17 wherein the polyol comprisingat least one terminal hydroxyl group comprises a polyester, a polyether,or a combination thereof.

Embodiment 19

The method of any one of Embodiments 1-18 wherein the polyestercomprises a compound resulting from condensation of phthalic anhydrideand di-ethylene glyol, phthalic anhydride and di-propylene glycol, oradipic acid and butane diol.

Embodiment 20

The method of any one of Embodiments 1-19 wherein the polyethercomprises a compound resulting from polymerization of an oxide selectedfrom ethylene oxide, propylene oxide, or butylene oxide, from aninitiator selected from glycerol, di-propylene glycol, TPG, castor oil,sucrose, or sorbitol.

Embodiment 21

The method of any one of Embodiments 1-20 wherein the polyol comprises amolecular weight of from 200 Daltons to 20,000 Daltons, such as from 200Daltons to 10,000 Daltons.

Embodiment 22

The method of any of Embodiments 1-21 wherein the first reactivecomponent comprises a prepolymer.

Embodiment 23

The method of any of Embodiments 1-22 wherein the prepolymer comprisesan isocyanate prepolymer that comprises less than 20% unreactedisocyanate groups

Embodiment 24

The method of any of Embodiments 1-23 wherein the isocyanate prepolymercomprises greater than 0.1% unreacted isocyanate groups.

Embodiment 25

The method of any of Embodiments 1-24 wherein the prepolymer comprises apolyol and/or amine prepolymer that comprises less than 14% unreactedalcohol groups.

Embodiment 26

The method of any of Embodiments 1-25 wherein the first and secondreactive components comprise at least one additive selected from acatalyst, a chain extender, a curing agent, a surfactant, a pigment, adye, a rheology modifier, a filler, or a combination thereof.

Embodiment 27

The method of any of Embodiments 1-26 wherein the first and secondreactive components each comprise a viscosity of at least 60 centipoise(cP).

Embodiment 28

The method of any of Embodiments 1-27 wherein the first and secondreactive components each comprise a viscosity from 500 cp to 500,000 cp.

Embodiment 29

The method of any of Embodiments 1-28 wherein the partially reactedthermoset product comprises a viscosity below 3,000,000 cP upon exitingthe mixing chamber.

Embodiment 30

The method of any of Embodiments 1-29 wherein the partially reactedthermoset product does not increase pressure present in the mixingchamber by more than 20% in 5 minutes.

Embodiment 31

The method of any of Embodiments 1-30 wherein the ratio of viscosity ofthe first and second reactive components is from 1:3 to 3:1.

Embodiment 32

The method of any of Embodiments 1-31 wherein the substrate comprises astage.

Embodiment 33

The method of any of Embodiments 1-32 wherein the substrate comprises apreviously formed and partially reacted thermoset product, or apreviously formed and completely reacted thermoset or thermoplasticproduct, or a metal product.

Embodiment 34

The method of any of Embodiments 1-33 wherein the 3D object comprisesmore than one type of material.

Embodiment 35

The method of any of Embodiments 1-34 wherein the 3D object comprises asolid thermoset product.

Embodiment 36

The method of any of Embodiments 1-35 wherein the solid thermosetproduct comprises a Shore A hardness of 20 to 120.

Embodiment 37

The method of any of Embodiments 1-36 wherein the solid thermosetproduct comprises a Shore D hardness of at least 30 to no greater than120.

Embodiment 38

The method of any of Embodiments 1-37 wherein the 3D object comprises afoam thermoset product.

Embodiment 39

The method of any of Embodiments 1-38 wherein the foam comprises a 25%IFD hardness of at least 15 lbs. to no greater than 60 lbs.

Embodiment 40

The method of any of Embodiments 1-39 wherein the foam comprises acompression resistance at 10% deflection of 25 to 200 kPa.

Embodiment 41

The method of any of Embodiments 1-40 wherein the foam comprises abending strength of 150 and 2000 kPa.

Embodiment 42

The method of any of Embodiments 1-41 wherein the foam comprises adensity of no less than 0.05 gram/milliliter (g/ml) to no greater than1.3 g/ml.

Embodiment 43

A 3D object comprising a completely reacted thermoset product, whereinthe completely reacted thermoset product comprises a solid thermosetproduct and a foam thermoset product, wherein a portion of the solidthermoset product and a portion of the foam thermoset product arecovalently bonded.

Embodiment 44

The 3D object of Embodiment 43 wherein the solid thermoset productcomprises a Shore A hardness of 20 to 120.

Embodiment 45

The 3D object of any of Embodiments 43 or 44 wherein the solid thermosetproduct comprises a Shore D hardness of at least 30 to no greater than120.

Embodiment 46

The 3D object of any of Embodiments 43-45 wherein the foam thermosetproduct comprises a 25% IFD hardness of at least 15 lbs. to no greaterthan 60 lbs.

Embodiment 47

The 3D object of any of Embodiments 43-46 wherein the foam comprises adensity of no less than 0.05 g/ml to no greater than 1.3 g/ml.

Embodiment 48

The 3D object of any of Embodiments 43-47 wherein the hardness of thefoam thermoset product varies between two separate areas of the foamthermoset product of the 3D object.

Embodiment 49

The 3D object of any of Embodiments 43-48 wherein the density of thefoam thermoset product varies between two separate areas of the foamthermoset product of the 3D object.

Embodiment 50

A 3D object comprising a completely reacted solid thermoset product,wherein the hardness of the completely reacted solid thermoset productvaries between two separate areas of the solid thermoset product of the3D object.

Embodiment 51

The 3D object of Embodiment 50 wherein the solid thermoset productcomprises a Shore A hardness of 20 to 120.

Embodiment 52

The 3D object of any of Embodiments 50 or 51 wherein the solid thermosetproduct comprises a Shore D hardness of at least 30 to no greater than120.

Embodiment 53

A 3D object comprising a completely reacted foam thermoset product,wherein the hardness of the completely reacted foam thermoset productvaries between two separate areas of the solid thermoset product of the3D object.

Embodiment 54

The 3D object of Embodiment 53 wherein the foam thermoset productcomprises a 25% IFD hardness of at least 15 lbs. to no greater than 60lbs.

Embodiment 55

A 3D object comprising a completely reacted foam thermoset product,wherein the density of the completely reacted foam thermoset productvaries between two separate areas of the solid thermoset product of the3D object.

Embodiment 56

The 3D object of Embodiment 55 wherein the foam comprises a density ofgreater than 0.05 g/ml to no greater than 1.3 g/ml.

Embodiment 57

The method of any of Embodiments 1-42 further comprising providing oneor more additional reactive components, wherein the one or moreadditional reactants are introduced into the mixing chamber.

Embodiment 58

The method of any of Embodiments 1-42 or 57 wherein introducing the oneor more additional reactive components results in a 3D object comprisinga property that varies between two separate areas of the 3D object.

Embodiment 59

The method of any of Embodiments 1-42, 57, or 58 wherein the propertythat varies comprises hardness, density, or a combination thereof.

Embodiment 60

The method of any of Embodiments 1-42 or 57-59 wherein the 3D objectcomprises a solid thermoset product.

Embodiment 61

The method of any of Embodiments 1-42 or 57-60 wherein the 3D objectcomprises a foam thermoset product.

Embodiment 62

The method of any of Embodiments 1-42 or 57-6139-43 wherein the 3Dobject comprises solid thermoset product and foam thermoset product.

Embodiment 63

A thermoset system comprising a first and a second reactive component,wherein the first component comprises a polyol and/or amine prepolymer,a fast reactant, and a slow reactant, wherein the first componentcomprises 1% to 10% fast reactant and 1% to 75% slow reactant, andwherein the second component comprises an isocyanate prepolymer thatcomprises a monomeric isocyanate.

Embodiment 64

The thermoset system of Embodiment 63 wherein the fast reactantcomprises a chain extender.

Embodiment 65

The thermoset system of Embodiment 63 or 64 wherein the chain extendercomprises a di-amine, water, a primary hydroxyl reaction group, or acombination thereof.

EXAMPLES

Liquid blends of isocyanate prepolymers and neat isocyanates wereprepared at various ratios to form an isocyanate component, and thenwere mixed with a formulation of polyols, amines, and catalysts. Themixture of the two components was extruded through a static mixer at agiven rate and residence time.

Final properties of the exiting materials were measured using a Shore Ahardness gauge. A viscosity profile was created using Brookfieldviscometer measurements utilizing different viscometer temperaturesettings and torque ranges to determine and predict the speed ofreaction of the formulated materials.

Monomeric MDI (Diphenymethane-4,4′-diisocyanate) was obtained from BASFCorporation (Lupranate MI). Technical grade TDI (80%Tolylene-2,4-diisocyanate, 20% Tolylene-2,6-diisocyanate) was obtainedfrom Sigma-Aldrich. Pluracol polyols were obtained from BASFCorporation. Ethacure 100 and Ethacure 300 amines were obtained fromAlbemarle Corporation.

Isocyanate Prepolymer Syntheses

-   -   Pluracol 1010 TDI Prepolymer: 72 wt % Pluracol 1010, 28% TDI.    -   Pluracol 2010 TDI Prepolymer: 83.6 wt % Pluracol 2010, 16.4%        TDI.    -   Pluracol 1010 MDI Prepolymer: 64 wt % Pluracol 1010, 36 wt %        Lupranate MI.    -   Pluracol 2010 MDI Prepolymer: 80% Pluracol 2010, 20% Lupranate        MI.

Isocyanate was heated in the reaction vessel to 80° C. Polyol was addedover two hours while maintaining the reaction temperature between 80 and85° C. Reaction vessel was maintained at 80° C. for an additional twohours. Reaction mixture was stirred and blanketed with nitrogenthroughout the reaction. At the end of the reaction, the mixture wascooled and poured into storage.

Polyol Prepolymer Synthesis

Polyol Prepolymer 1: Pluracol polyol was heated to 80° C. Isocyanateaddition rate was set to add entire amount over two hours. After 75minutes, butanediol addition was commenced such that the butanediol wasadded over 45 minutes. After addition was completed, reaction mixturewas held for two hours. During entire reaction, temperature was heldbetween 80 and 85° C. Reaction mixture was stirred and blanketed withnitrogen through the reaction. At the end of the reaction, the mixturewas cooled and poured into storage.

Composition was 62% Pluracol 1010, 26.8% Lupranate MI, 11.2% butanediol.

Polyol Prepolymer 2: Butanediol was heated to 80° C. Isocyanateprepolymer was added over two hours. Reaction mixture was held for twohours. During entire reaction, temperature was held between 80 and 85°C. Reaction mixture was stirred and blanketed with nitrogen through thereaction. At the end of the reaction, the mixture was cooled and pouredinto storage.

Composition was 12% butanediol, 88% P1 1010 MDI prepolymer.

Mixing Properties

An isocyanate formula and a polyol were loaded into syringes and pumpedthrough a junction to a static mixer. At the end of the static mixer,the combined materials flowed through a nozzle. The static mixer had avolume of 2.37 mL and included 12 mixing elements. Total flow rates werevaried from 2 to 8 mL/min.

The examples below show that the relative viscosities of the componentformulas affected the quality of the mixing in the static mixer. Mixingquality was rated from 1 to 3. Mixing rated as a “1” was poor: visualobservations of the material inside the mixer and exiting the mixershowed distinct material separation. Mixing rated as a “2” appearedmixed upon exiting the mixer, but the final part had a noticeable swirlpattern and had a liquid residue on the surface. Mixing rated as a “3”was excellent: the completely reacted material cured and had finalproperties indistinguishable from material that was vigorously mixed ina cup and cured.

The isocyanate formula was either straight prepolymer or a blend ofmonomeric isocyanate and an isocyanate prepolymer. The polyol formulawas a blend of amine, polyol, and catalyst. In Example 1, an isocyanateformula with a viscosity of 8000 cps was mixed with a polyol formulawith a viscosity of 100 cps, and showed poor mixing. In Example 5, anisocyanate formula with viscosity of 7000 cps and a polyol formula withviscosity of 2500 cps showed excellent mixing.

TABLE 1 Prepolymer Isocyanate Polyol formula Reference Isocyanate Mixformula viscosity viscosity Mixing Example Number Type/Mix ratio (CPS)(CPS) Quality result 1 C3DM1-38 TDI 100%  6.32:1 8000 100 1 2 C3DM1-40TDI 100% 10.25:1 5000 (25° C.) 100 1 3 C3DM1-43 TDI 100% 10.25:1 1000(50° C.) 100 2 4 C3DM1-70 MDI 80/20    1:1.2 7000 100 1 5 C3DM4-22 MDI80/20  1.1:1 7000 2500 3

TABLE 2 Formulas C3DM1-38 C3DM1-40 C3DM1-43 C3DM1-70 C3DM4-22 A-side PI1010 TDI  100% prepolymer PI 2010 TDI 100% 100% prepolymer PI 1010 MDI79.7%   80% prepolymer MDI 20.3%   20% B-side Ethacure 300 23.8%Ethacure 100 69.2% 100% 100%  5.0%  7.2% PI 1010  7.0% 93.2% 64.0%Polyol 27.5% prepolymer 2 Dabco 33LX  1.0%  0.7% Dabco T12  0.8%  0.6%

Viscometer settings: Isocyanate formulas C3DM1-38,40,43 used spindle 31at 6 RPM. Formulas C3DM1-70 and C3DM4-22 used spindle 27 at 6 RPM. Allmeasurements at 20° C. except for sample C3DM1-43 which was measured at50° C. Polyol formulas C3DM1-38, 40, 43, 70 were measured at 20° C., 30RPM, Spindle 18. Polyol formula for C3DM4-22 used spindle 27 at 20° C.,6 RPM.

Viscosity Growth During Cure

Viscosity growth rate during cure is a useful parameter for achievingprintable materials.

Examples below show that different formulas yield different viscosityprofiles after being mixed. Formulation changes related to theconcentration of reactive groups, reactivity of formula components, andcatalyst levels can independently affect the growth of viscosity duringcure.

The viscosity profiles were measured by rapidly mixing the two formulacomponents, pouring 10 grams of the reacting mixture into a Brookfieldviscometer sample cup, and then recording the viscosity as a function oftime.

Examples 1 and 2 Pure Isocyanate Vs Prepolymer

In the first example, the formula (C3DM1-85) used an isocyanate formulawith Toluene di isocyanate (TDI) 87 g/mol of isocyanate. The isocyanateformula was reacted with a mixture of Ethacure 100 and Pluracol 201f0,with a reaction equivalent density of 482 g/mol. The isocyanate andpolyol formulas were mixed with a ratio of 1:5.28 for a 4%stoichiometric excess of isocyanate.

In the second example, the formula (C3DM1-81) used an isocyanate formulawith 870 g/mol isocyanate. This isocyanate formula contained aprepolymer made by reacting Pluracol 2010 with MDI with the entirepolyol content of the first reaction pre-reacted with the isocyanate.This formula was reacted with an amine Ethacure 100 with a reactionequivalent density of 89 g/mol. The isocyanate and amine chain extenderformulas were mixed with a ratio of 10.2:1 for a 4% stoichiometricexcess of isocyanate.

Example 1 had a very high density of highly labile isocyanate groups,and cured very quickly, while Example 2 had a density of isocyanategroups which is ten times lower, and cured much more slowly. Theformulas used are given below:

TABLE 3 C3DM1-85 Amount(g) A-side TDI 1.93 B-side PL2010 polyol 9.16Ethacure 100 1.04

TABLE 4 C3DM1-81 Amount(g) A-side PL2010 TDI 15.48 prepolymer B-sideEthacure 100 1.52

TABLE 5 Example 1 Example 2 C3DM1-85 C3DM1-81 Time Viscosity Viscosity(min) (cps) (cps) 0 1,000 5,000 1 300,000 1.5 780,000 2 cured 5650 311,000 4 34,100 5 59,000 6 91,000 10 708,000

Viscometer settings: 22° C., 0.3 RPM, spindle 27.

Examples 3 and 4 Effect of Catalyst

These examples show the effect of different catalyst on the cure rate.Example 3 (C3DM-86) had a different catalyst than Example 4 (C3DM1-102).Samples with different catalysts were mixed and poured into a Brookfieldviscosity cup, in a temperature chamber set at 22° C., and themeasurements were taken at the time intervals. The formulas used aregiven below:

TABLE 6 C3DM1-86 Amount(g) A-side PL2010 TDI 16.04 prepolymer B-sideEthacure 100 1.56 Dabco 33LX 0.049

TABLE 7 C3DM1-102 Amount(g) A-side PL2010 TDI 15.02 prepolymer B-sidePL2010 polypl 3.49 Ethacure 100 1.177 KKAT XK-618 0.205

TABLE 8 Example 3 Example 4 C3DM1-86 C3DM1-102 Time Viscosity Viscosity(min) (cps) (cps) 0 5,000 5,000 2 25,500 12,500 3 66,700 12,500 4210,000 12,500 5 569,000 12,500 6 cured 13,333 7 33,500 8 48,333 10145,000 11 240,000 12 398,000

Viscometer settings: 22° C., 0.3 RPM, spindle 27.

Example 5 Effect of Temperature on Cure Rate

Identical samples were prepared and the viscosity growth was measured at22° C. and 50° C. To record viscosity at the higher temperature, theinitial components were heated to 50° C., mixed, and then poured into aviscometer cup with a temperature-control jacket plumbed to acirculating bath. The formulas used are given below:

TABLE 9 C3DM1-99 Amount(g) A-side PL2010 TDI 16.01 prepolymer B-sideEthacure 100 1.5732 KKAT XK618 0.0855

TABLE 10 C3DM1-100 Amount(g) A-side PL2010 TDI 18.015 prepolymer B-sideEthacure 100 1.7853 KKAT XK618 0.1222

TABLE 11 C3DM1-99 22° C. C3DM1-100 Time Viscosity 50° (min) (cps) (cps)2 36,500 2.5 39,167 56,600 3 40,000 85,000 4 41,667 112,000 5 86,333278,000 6 142,000 534,000 7 250,000 cured 8 459,000 9 793,000

Viscometer settings: 22° C., 0.3 RPM, spindle 27. The prepolymer forformula C3DM1-100 was heated to 50° C. before use.

Example 6 Example of Effect of Different Isocyanate Prepolymers on CureRate

Two isocyanate formulas were reacted with an identical polyol formula.The isocyanate formula for C3DM4-50 had 20% TDI (toluene di-isocyanate)and 80% Pluracol 1010 TDI prepolymer. The isocyanate formula forC3DM4-28 had 20% monomeric MDI and 80% Pluracol 1010 MDI prepolymer.Each were mixed with a 5% stoichiometric excess of the polyol formula.

The isocyanate groups on TDI do not have equivalent reactivities,whereas the isocyanate groups on MDI have equivalent reactivity. It wasobserved that the TDI-based formula had a rapid increase in viscosity,followed by a plateau, whereas the MDI-based formula had a more steadyincrease in viscosity (FIG. 2). The formulas used are given below:

TABLE 12 C3DM4-50 Amount(g) A-side PL1010 TDI 24.03 prepolymer TDI 6.01B-side PL1010 polyol 19.77 Polyol Prepolymer 2 10.67 Ethacure 100 0.88Ethacure 300 3.69 KKAT XK618 0.19

TABLE 13 C3DM4-28 Amount(g) A-side PL1010 MDI 12.05 prepolymer MDI 3.03B-side PL1010 polyol 7.99 Polyol Prepolymer 1 4.31 Ethacure 100 0.36Ethacure 300 1.49 KKAT XK618 0.11

Example 7 Printability and Mixer Residence Time

In this example, we demonstrate how the viscosity growth rate of twopartially reacted thermosets interact with the volumetric flow rate andvolume of the mixer to define a set of flow rates for which thepartially reacted thermosets are printable. Both formulas produce apolymer with a Shore A hardness of approximately 50. The formulas usedare given below:

TABLE 14 Fast formula Isocyanate Wt % Polyol Wt % Lupranate MI 20Ethacure 100 8.5 P11010 MDI 80 Pluracol 1010 59 prepolymer Polyolprepolymer 2 32 Dabco T12 0.25 Dabco 33LX 0.25 Starting viscosity 5300cp 2660 cp Spindle 27, 6 RPM 25° C. 20° C.

TABLE 15 Slow formula Isocyanate Wt % Polyol Wt % Lupranate MI 20Ethacure 100 3.5 Ethacure 300 7.0 P11010 MDI 80 Pluracol 1010 58prepolymer Polyol prepolymer 2 31 KKat XK-618 0.5 Starting viscosity5300 cp 2500 cp Spindle 27, 6 RPM 25° C. 20° C.

The fast formula system cures too quickly to measure viscosity growth.In the 30 seconds that it takes to mix, the material solidifies too muchto pour into the viscometer cup.

The viscosity growth of the slow formula system is shown in FIG. 3. Theviscosity increases two orders of magnitude, to approximately 1,000,000cps, in 3 minutes. Viscometer settings: 22° C., spindle 27, 0.3 RPM.

To illustrate the processing window of the formulas, we printed a singlelayer circle at various flow rates (FIG. 4 and FIG. 5). The twocomponents had a mix ratio of 1:1, and were pumped through a staticmixer nozzle with a volume of 250 μL. For the fast formula, below 500mm/min (FIG. 4, upper circle in column 1, and all circles in column 2)(400 μL/min, 37.5 sec residence time) the flow stops, and above 2500mm/min (FIG. 4, lower circle in column 3 and all circles in the 6^(th)column) (2000 μL/min, 7.5 sec residence time), the line thickness variesand then spreads. The fast formula had a processing window spanningresidence times ranging from 7.5-37.5 seconds. For the slow formula,below 250 mm/min (FIG. 5, upper circle in column 1 and all circles incolumn 2) (200 μL/min, 75 sec residence time), the flow stops, and above2000 mm/min (FIG. 5, middle circle in column 3 and lower circle incolumn 4) (1600 μL/min, 9.4 sec residence time), the line thicknessvaries. The slow formula had a broader processing window spanning 9.4-75seconds.

Example 8 Multi-Layer Printing

Formula C3DM4-71 was printed on a Hyrel 3D printer. The printerparameters were set such that material was pumped through the mixer at1296 μL/min. The mixer had a volume of approximately 250 and a tipnozzle diameter of 0.8 mm. Three adjacent concentric circles weredeposited on the printing surface, and subsequent layers werecontinually deposited for a total of 29 layers (FIG. 6). After theprinting process, the structure was heated in a 50° C. oven for 30minutes. The formula used is given below:

TABLE 16 C3DM4-71 Amount(g) A-side PL1010 MDI 80 prepolymer MDI 20B-side PL1010 polyol 71.17 Polyol prepolymer 1 20.63 Ethacure 100 4.18Ethacure 300 7.33 KKAT XK618 0.70

Example 9 Foam Printing

Formula C3DM4-64 was printed on a Hyrel 3D printer. The printerparameters were set such that material was pumped through the mixer at450 μL/min. The mixer had a volume of approximately 1000 and a tipnozzle diameter of 1.75 mm. Three adjacent concentric circles weredeposited on the printing surface, and subsequent layers werecontinually deposited for a total of 70 layers. As the layers weredeposited, lower layers foamed and expanded. The formula used is givenbelow:

TABLE 17 Formula C3DM4-64 Isocyanate Wt % Polyol Wt % Lupranate MI 40Ethacure 300 2.1 Pluracol 1010 MDI 60 Ethacure 100 2.1 prepolymer water4 Pluracol 2010 16.75 Pluracol 1135i 75 Stannous Octanoate 0.6 Dabco DC5043 0.4

Example 10 Print Parameter Effects on Part Geometry

A hollow cylinder of formula C3DM4-105 was printed by continuouslydepositing a single circle of material on a printing platform. A SulzerMixpac Statomix EA3.0-13SA 13 element static mixer was attached to a 1:1dual cartridge which was controlled by the printer. For each part, 20layers were deposited. Parameters such as the time per layer and thevolumetric flow rate of the partially reacted thermoset product wereseen to impact the final part geometry. These parameters can becontrolled to achieve the desired part resolution.

TABLE 18 Printhead volumetric Band Linear Part Band Time Per flow rateDiameter Speed Height Thickness Layer (microliter/ (mm) (mm/min) (mm)(mm) (sec) sec) 100 800 7.9 4.2 25 86.4 100 500 9.6 3.2 38 54 100 35011.2 2.9 54 37.8 100 250 11.7 2.6 75 27 90 350 10.8 3.0 49 37.8 80 35010.3 3.0 45 37.8 70 350 10.0 3.2 38 37.8 60 350 9.8 3.4 33 37.8 50 3509.0 3.6 27 37.8 30 350 7.3 4.6 17 37.8 20 350 6.1 Flowed part 11 37.8 10350 4.5 Flowed part 6 37.8

TABLE 19 Formula C3DM4-105 Isocyanate Wt % Polyol Wt % Lupranate MI 20Ethacure 300  7.0% Pluracol 1010 MDI 80 Ethacure 100  4.0% prepolymerPluracol 1010 66.8% Pluracol 1135i 10.0% Polyol Prepolymer 1 12.0% KKatXK-618  0.2%

Example 11 Part Density

Formula C3DM8-49 was extruded onto a rectangular mold using a 3MScotch-Weld EPX Plus II Manual Applicator. The rectangular part cured atroom temperature for 48 hours, and then was cured in an oven at 60° C.for 6 hours. A part was cut from the sample, was weighed for mass, andthen volume was measured by displacement of water in a volumetric flask.Density was recorded as mass divided by volume. The density of the partwas 1.12+/−0.01 g/mL.

Formula C3DM8-49 was printed using a Hyrel printer with a 2504, mixingvolume tip with a 0.8 mm nozzle diameter. The printed part dimensionswere a 50.8 mm×127 mm×3 layers. The line widths were set to 1.6 mm, andwere printed with paths separated by 1.0 mm. The translation speed was1000 mm/min and the flow multiplier was set to 3.0. The density of thepart was 1.12+/−0.01 g/mL.

Example 12 Formula Variations to Achieve Changes in Part Hardness

The formulas in Table 20 were formulated to with a fixed number ofingredients to achieve a range of Shore A Hardnesses.

TABLE 20 Formula Name C3DM8-47 C3DM8-36 C3DM8-51 C3DM8-41 C3DM8-58 ShoreA Hardness 36 37 50 64 90 A:B Volumetric Ratio 1:1 1:1 1:1 1:1 1:1Amount Amount Amount Amount Amount (wt %) (wt %) (wt %) (wt %) (wt %)A-side PL1010 MDI 90.0 80.0 65.0 prepolymer PL2010 MDI 80.0 80.0prepolymer Lupranate MI 20.0 10.0 20.0 20.0 35.0 B-side PL1010 polyol65.9 62.5 52.0 60.5 46.3 PL2010 polyol 20.2 10.0 Pluracol 11351 7.9 10.09.9 Polyol Prepolymer 2 20.9 12.2 21.2 17.9 28.6 Ethacure 100 3.0 5.05.0 4.5 Ethacure 300 2.0 1.5 6.9 25 Color 0.2 0.2 0.2 KKAT XK618 0.1 0.10.1 0.1 0.1

The complete disclosure of all patents, patent applications, andpublications, and electronically available material cited herein areincorporated by reference in their entirety. Supplementary materialsreferenced in publications (such as supplementary tables, supplementaryfigures, supplementary materials and methods, and/or supplementaryexperimental data) are likewise incorporated by reference in theirentirety. In the event that any inconsistency exists between thedisclosure of the present application and the disclosure(s) of anydocument incorporated herein by reference, the disclosure of the presentapplication shall govern. The foregoing detailed description andexamples have been given for clarity of understanding only. Nounnecessary limitations are to be understood therefrom. The invention isnot limited to the exact details shown and described, for variationsobvious to one skilled in the art will be included within the inventiondefined by the claims.

Unless otherwise indicated, all numbers expressing quantities ofcomponents, molecular weights, and so forth used in the specificationand claims are to be understood as being modified in all instances bythe term “about.” Accordingly, unless otherwise indicated to thecontrary, the numerical parameters set forth in the specification andclaims are approximations that may vary depending upon the desiredproperties sought to be obtained by the present invention. At the veryleast, and not as an attempt to limit the doctrine of equivalents to thescope of the claims, each numerical parameter should at least beconstrued in light of the number of reported significant digits and byapplying ordinary rounding techniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. All numerical values, however, inherently contain a rangenecessarily resulting from the standard deviation found in theirrespective testing measurements.

All headings are for the convenience of the reader and should not beused to limit the meaning of the text that follows the heading, unlessso specified.

1. A method of creating a three dimensional (3D) object from reactivecomponents that form a thermoset product using extruded thermosetprinting, comprising: providing a first reactive component and a secondreactive component that are effective to form a thermoset product havinga predetermined layer resolution during the method; introducing thefirst reactive component and the second reactive component into a mixingchamber where mixing occurs to form a mixture, wherein the firstreactive component, the second reactive component, or the first reactivecomponent and the second reactive component contains a fast reactant anda slow reactant, wherein the first reactive component, the secondreactive component, or the first reactive component and the secondreactive component contains 1% to 10% fast reactant and 1% to 75% slowreactant, wherein the first reactive component and the second reactivecomponent have a residence time in the mixing chamber effective to forma partially reacted thermoset product in the mixing chamber and resultin the predetermined layer resolution upon exiting the mixing chamber,and wherein the first reactive component and the second reactivecomponent have a residence time in the mixing chamber insufficient tocompletely react; extruding the partially reacted thermoset product outof the mixing chamber through an extrusion nozzle and onto a substrate;and moving the extrusion nozzle and/or the substrate to form a 3D objecthaving a predetermined shape resolution.
 2. The method of claim 1wherein the thermoset product comprises a urethane and/orurea-containing polymer.
 3. The method of claim 2 wherein the firstreactive component comprises an isocyanate, wherein the second reactivecomponent comprises a polyol comprising at least one terminal hydroxylgroup, a polyamine comprising at least one amine that comprises anisocyanate reactive hydrogen, or a combination of the polyol and thepolyamine.
 4. The method of claim 1 wherein the first reactive componentcomprises a prepolymer.
 5. The method of claim 4 wherein the prepolymercomprises an isocyanate prepolymer that comprises less than 20%unreacted isocyanate groups
 6. (canceled)
 7. (canceled)
 8. The method ofclaim 1 wherein the first reactive component and the second reactivecomponent comprise at least one additive selected from a catalyst, achain extender, a curing agent, a surfactant, a pigment, a dye, arheology modifier, a filler, or a combination thereof. 9-12. (canceled)13. The method of claim 1 wherein the ratio of viscosity of the firstreactive component and the second reactive component is from 1:3 to 3:1.14. The method of claim 1 wherein the substrate comprises a stage. 15.The method of claim 14 wherein the substrate comprises a previouslyformed and partially reacted thermoset product, a previously formed andcompletely reacted thermoset or thermoplastic product, or a metalproduct.
 16. The method of claim 1 wherein the 3D object comprises morethan one type of material.
 17. The method of claim 1 wherein the 3Dobject comprises a solid thermoset product.
 18. (canceled) 19.(canceled)
 20. The method of claim 1 wherein the 3D object comprises afoam thermoset product.
 21. (canceled)
 22. The method of claim 20wherein the foam comprises a compression resistance at 10% deflection of25 to 200 kPa.
 23. (canceled)
 24. The method of claim 20 wherein thefoam comprises a density of no less than 0.05 gram/milliliter (g/ml) tono greater than 1.3 g/ml.
 25. A 3D object comprising a completelyreacted thermoset product, wherein the completely reacted thermosetproduct comprises a solid thermoset product and a foam thermosetproduct, wherein a portion of the solid thermoset product and a portionof the foam thermoset product are covalently bonded. 26-29. (canceled)30. The 3D object of claim 25 wherein the hardness of the foam thermosetproduct varies between two separate areas of the foam thermoset productof the 3D object.
 31. The 3D object of claim 25 wherein the density ofthe foam thermoset product varies between two separate areas of the foamthermoset product of the 3D object. 32-38. (canceled)
 39. The method ofclaim 1 further comprising providing one or more additional reactivecomponents, wherein the one or more additional reactants are introducedinto the mixing chamber. 40-44. (canceled)
 45. A thermoset systemcomprising a first reactive component and a second reactive component,wherein the first reactive component comprises a polyol and/or amineprepolymer, a fast reactant, and a slow reactant, wherein the firstreactive component comprises 1% to 10% fast reactant and 1% to 75% slowreactant, and wherein the second reactive component comprises anisocyanate prepolymer that comprises a monomeric isocyanate.
 46. Thethermoset system of claim 45 wherein the fast reactant comprises a chainextender.
 47. (canceled)